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krahets
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<li class="md-nav__item">
<a href="#733" class="md-nav__link">
7.3.3 &nbsp;与局限性
7.3.3 &nbsp;与局限性
</a>
</li>
@@ -3335,7 +3335,7 @@
<li class="md-nav__item">
<a href="#733" class="md-nav__link">
7.3.3 &nbsp;与局限性
7.3.3 &nbsp;与局限性
</a>
</li>
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<!-- Page content -->
<h1 id="73">7.3 &nbsp; 二叉树数组表示<a class="headerlink" href="#73" title="Permanent link">&para;</a></h1>
<p>在链表表示下,二叉树的存储单元为节点 <code>TreeNode</code> ,节点之间通过指针相连接。在上节中,我们学习了在链表表示下的二叉树的各项基本操作。</p>
<p>在链表表示下,二叉树的存储单元为节点 <code>TreeNode</code> ,节点之间通过指针相连接。上一节介绍了链表表示下的二叉树的各项基本操作。</p>
<p>那么,我们能否用数组来表示二叉树呢?答案是肯定的。</p>
<h2 id="731">7.3.1 &nbsp; 表示完美二叉树<a class="headerlink" href="#731" title="Permanent link">&para;</a></h2>
<p>先分析一个简单案例。给定一完美二叉树,我们将所有节点按照层序遍历的顺序存储在一个数组中,则每个节点都对应唯一的数组索引。</p>
<p>根据层序遍历的特性,我们可以推导出父节点索引与子节点索引之间的“映射公式”:<strong>若节点的索引为 <span class="arithmatex">\(i\)</span> ,则该节点的左子节点索引为 <span class="arithmatex">\(2i + 1\)</span> ,右子节点索引为 <span class="arithmatex">\(2i + 2\)</span></strong> 。图 7-12 展示了各个节点索引之间的映射关系。</p>
<p>先分析一个简单案例。给定一完美二叉树,我们将所有节点按照层序遍历的顺序存储在一个数组中,则每个节点都对应唯一的数组索引。</p>
<p>根据层序遍历的特性,我们可以推导出父节点索引与子节点索引之间的“映射公式”:<strong>节点的索引为 <span class="arithmatex">\(i\)</span> ,则该节点的左子节点索引为 <span class="arithmatex">\(2i + 1\)</span> ,右子节点索引为 <span class="arithmatex">\(2i + 2\)</span></strong> 。图 7-12 展示了各个节点索引之间的映射关系。</p>
<p><a class="glightbox" href="../array_representation_of_tree.assets/array_representation_binary_tree.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="完美二叉树的数组表示" class="animation-figure" src="../array_representation_of_tree.assets/array_representation_binary_tree.png" /></a></p>
<p align="center"> 图 7-12 &nbsp; 完美二叉树的数组表示 </p>
<p><strong>映射公式的角色相当于链表中的指针</strong>。给定数组中的任意一个节点,我们都可以通过映射公式来访问它的左(右)子节点。</p>
<h2 id="732">7.3.2 &nbsp; 表示任意二叉树<a class="headerlink" href="#732" title="Permanent link">&para;</a></h2>
<p>完美二叉树是一个特例,在二叉树的中间层通常存在许多 <span class="arithmatex">\(\text{None}\)</span> 。由于层序遍历序列并不包含这些 <span class="arithmatex">\(\text{None}\)</span> ,因此我们无法仅凭该序列来推测 <span class="arithmatex">\(\text{None}\)</span> 的数量和分布位置。<strong>这意味着存在多种二叉树结构都符合该层序遍历序列</strong></p>
<p>如图 7-13 所示,给定一非完美二叉树,上述数组表示方法已经失效。</p>
<p>如图 7-13 所示,给定一非完美二叉树,上述数组表示方法已经失效。</p>
<p><a class="glightbox" href="../array_representation_of_tree.assets/array_representation_without_empty.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="层序遍历序列对应多种二叉树可能性" class="animation-figure" src="../array_representation_of_tree.assets/array_representation_without_empty.png" /></a></p>
<p align="center"> 图 7-13 &nbsp; 层序遍历序列对应多种二叉树可能性 </p>
<p>为了解决此问题,<strong>我们可以考虑在层序遍历序列中显式地写出所有 <span class="arithmatex">\(\text{None}\)</span></strong> 。如图 7-14 所示,这样处理后,层序遍历序列就可以唯一表示二叉树了。</p>
<p>为了解决此问题,<strong>我们可以考虑在层序遍历序列中显式地写出所有 <span class="arithmatex">\(\text{None}\)</span></strong> 。如图 7-14 所示,这样处理后,层序遍历序列就可以唯一表示二叉树了。示例代码如下:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="1:12"><input checked="checked" id="__tabbed_1_1" name="__tabbed_1" type="radio" /><input id="__tabbed_1_2" name="__tabbed_1" type="radio" /><input id="__tabbed_1_3" name="__tabbed_1" type="radio" /><input id="__tabbed_1_4" name="__tabbed_1" type="radio" /><input id="__tabbed_1_5" name="__tabbed_1" type="radio" /><input id="__tabbed_1_6" name="__tabbed_1" type="radio" /><input id="__tabbed_1_7" name="__tabbed_1" type="radio" /><input id="__tabbed_1_8" name="__tabbed_1" type="radio" /><input id="__tabbed_1_9" name="__tabbed_1" type="radio" /><input id="__tabbed_1_10" name="__tabbed_1" type="radio" /><input id="__tabbed_1_11" name="__tabbed_1" type="radio" /><input id="__tabbed_1_12" name="__tabbed_1" type="radio" /><div class="tabbed-labels"><label for="__tabbed_1_1">Python</label><label for="__tabbed_1_2">C++</label><label for="__tabbed_1_3">Java</label><label for="__tabbed_1_4">C#</label><label for="__tabbed_1_5">Go</label><label for="__tabbed_1_6">Swift</label><label for="__tabbed_1_7">JS</label><label for="__tabbed_1_8">TS</label><label for="__tabbed_1_9">Dart</label><label for="__tabbed_1_10">Rust</label><label for="__tabbed_1_11">C</label><label for="__tabbed_1_12">Zig</label></div>
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@@ -3494,7 +3494,7 @@
<p><a class="glightbox" href="../array_representation_of_tree.assets/array_representation_complete_binary_tree.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="完全二叉树的数组表示" class="animation-figure" src="../array_representation_of_tree.assets/array_representation_complete_binary_tree.png" /></a></p>
<p align="center"> 图 7-15 &nbsp; 完全二叉树的数组表示 </p>
<p>以下代码实现了一基于数组表示的二叉树,包括以下几种操作。</p>
<p>以下代码实现了一基于数组表示的二叉树,包括以下几种操作。</p>
<ul>
<li>给定某节点,获取它的值、左(右)子节点、父节点。</li>
<li>获取前序遍历、中序遍历、后序遍历、层序遍历序列。</li>
@@ -4071,7 +4071,7 @@
<a id="__codelineno-18-31" name="__codelineno-18-31" href="#__codelineno-18-31"></a>
<a id="__codelineno-18-32" name="__codelineno-18-32" href="#__codelineno-18-32"></a><span class="w"> </span><span class="cm">/* 获取索引为 i 节点的父节点的索引 */</span>
<a id="__codelineno-18-33" name="__codelineno-18-33" href="#__codelineno-18-33"></a><span class="w"> </span><span class="nx">parent</span><span class="p">(</span><span class="nx">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<a id="__codelineno-18-34" name="__codelineno-18-34" href="#__codelineno-18-34"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nb">Math</span><span class="p">.</span><span class="nx">floor</span><span class="p">((</span><span class="nx">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mf">1</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 向下</span>
<a id="__codelineno-18-34" name="__codelineno-18-34" href="#__codelineno-18-34"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nb">Math</span><span class="p">.</span><span class="nx">floor</span><span class="p">((</span><span class="nx">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mf">1</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 向下整</span>
<a id="__codelineno-18-35" name="__codelineno-18-35" href="#__codelineno-18-35"></a><span class="w"> </span><span class="p">}</span>
<a id="__codelineno-18-36" name="__codelineno-18-36" href="#__codelineno-18-36"></a>
<a id="__codelineno-18-37" name="__codelineno-18-37" href="#__codelineno-18-37"></a><span class="w"> </span><span class="cm">/* 层序遍历 */</span>
@@ -4155,7 +4155,7 @@
<a id="__codelineno-19-31" name="__codelineno-19-31" href="#__codelineno-19-31"></a>
<a id="__codelineno-19-32" name="__codelineno-19-32" href="#__codelineno-19-32"></a><span class="w"> </span><span class="cm">/* 获取索引为 i 节点的父节点的索引 */</span>
<a id="__codelineno-19-33" name="__codelineno-19-33" href="#__codelineno-19-33"></a><span class="w"> </span><span class="nx">parent</span><span class="p">(</span><span class="nx">i</span><span class="o">:</span><span class="w"> </span><span class="kt">number</span><span class="p">)</span><span class="o">:</span><span class="w"> </span><span class="kt">number</span><span class="w"> </span><span class="p">{</span>
<a id="__codelineno-19-34" name="__codelineno-19-34" href="#__codelineno-19-34"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nb">Math</span><span class="p">.</span><span class="nx">floor</span><span class="p">((</span><span class="nx">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mf">1</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 向下</span>
<a id="__codelineno-19-34" name="__codelineno-19-34" href="#__codelineno-19-34"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nb">Math</span><span class="p">.</span><span class="nx">floor</span><span class="p">((</span><span class="nx">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mf">1</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 向下整</span>
<a id="__codelineno-19-35" name="__codelineno-19-35" href="#__codelineno-19-35"></a><span class="w"> </span><span class="p">}</span>
<a id="__codelineno-19-36" name="__codelineno-19-36" href="#__codelineno-19-36"></a>
<a id="__codelineno-19-37" name="__codelineno-19-37" href="#__codelineno-19-37"></a><span class="w"> </span><span class="cm">/* 层序遍历 */</span>
@@ -4497,7 +4497,7 @@
</div>
</div>
</div>
<h2 id="733">7.3.3 &nbsp;与局限性<a class="headerlink" href="#733" title="Permanent link">&para;</a></h2>
<h2 id="733">7.3.3 &nbsp;与局限性<a class="headerlink" href="#733" title="Permanent link">&para;</a></h2>
<p>二叉树的数组表示主要有以下优点。</p>
<ul>
<li>数组存储在连续的内存空间中,对缓存友好,访问与遍历速度较快。</li>
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<h1 id="75-avl">7.5 &nbsp; AVL 树 *<a class="headerlink" href="#75-avl" title="Permanent link">&para;</a></h1>
<p>在二叉搜索树章节中,我们提到在多次插入和删除操作后,二叉搜索树可能退化为链表。这种情况下,所有操作的时间复杂度将从 <span class="arithmatex">\(O(\log n)\)</span> 恶化为 <span class="arithmatex">\(O(n)\)</span></p>
<p>如图 7-24 所示,经过两次删除节点操作,这二叉搜索树便会退化为链表。</p>
<p>二叉搜索树章节中,我们提到在多次插入和删除操作后,二叉搜索树可能退化为链表。这种情况下,所有操作的时间复杂度将从 <span class="arithmatex">\(O(\log n)\)</span> 恶化为 <span class="arithmatex">\(O(n)\)</span></p>
<p>如图 7-24 所示,经过两次删除节点操作,这二叉搜索树便会退化为链表。</p>
<p><a class="glightbox" href="../avl_tree.assets/avltree_degradation_from_removing_node.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="AVL 树在删除节点后发生退化" class="animation-figure" src="../avl_tree.assets/avltree_degradation_from_removing_node.png" /></a></p>
<p align="center"> 图 7-24 &nbsp; AVL 树在删除节点后发生退化 </p>
<p>再例如,在图 7-25 的完美二叉树中插入两个节点后,树将严重向左倾斜,查找操作的时间复杂度也随之恶化。</p>
<p>再例如,在图 7-25 所示的完美二叉树中插入两个节点后,树将严重向左倾斜,查找操作的时间复杂度也随之恶化。</p>
<p><a class="glightbox" href="../avl_tree.assets/avltree_degradation_from_inserting_node.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="AVL 树在插入节点后发生退化" class="animation-figure" src="../avl_tree.assets/avltree_degradation_from_inserting_node.png" /></a></p>
<p align="center"> 图 7-25 &nbsp; AVL 树在插入节点后发生退化 </p>
<p>G. M. Adelson-Velsky 和 E. M. Landis 在其 1962 年发表的论文 "An algorithm for the organization of information" 中提出了「AVL 树」。论文中详细描述了一系列操作,确保在持续添加和删除节点后,AVL 树不会退化,从而使得各种操作的时间复杂度保持在 <span class="arithmatex">\(O(\log n)\)</span> 级别。换句话说,在需要频繁进行增删查改操作的场景中,AVL 树能始终保持高效的数据操作性能,具有很好的应用价值。</p>
<p>1962 年 G. M. Adelson-Velsky 和 E. M. Landis 在论文 "An algorithm for the organization of information" 中提出了「AVL 树」。论文中详细描述了一系列操作,确保在持续添加和删除节点后,AVL 树不会退化,从而使得各种操作的时间复杂度保持在 <span class="arithmatex">\(O(\log n)\)</span> 级别。换句话说,在需要频繁进行增删查改操作的场景中,AVL 树能始终保持高效的数据操作性能,具有很好的应用价值。</p>
<h2 id="751-avl">7.5.1 &nbsp; AVL 树常见术语<a class="headerlink" href="#751-avl" title="Permanent link">&para;</a></h2>
<p>AVL 树既是二叉搜索树也是平衡二叉树,同时满足这两类二叉树的所有性质,因此也被称为「平衡二叉搜索树 balanced binary search tree」。</p>
<h3 id="1">1. &nbsp; 节点高度<a class="headerlink" href="#1" title="Permanent link">&para;</a></h3>
<p>由于 AVL 树的相关操作需要获取节点高度,因此我们需要为节点类添加 <code>height</code> 变量</p>
<p>由于 AVL 树的相关操作需要获取节点高度,因此我们需要为节点类添加 <code>height</code> 变量</p>
<div class="tabbed-set tabbed-alternate" data-tabs="1:12"><input checked="checked" id="__tabbed_1_1" name="__tabbed_1" type="radio" /><input id="__tabbed_1_2" name="__tabbed_1" type="radio" /><input id="__tabbed_1_3" name="__tabbed_1" type="radio" /><input id="__tabbed_1_4" name="__tabbed_1" type="radio" /><input id="__tabbed_1_5" name="__tabbed_1" type="radio" /><input id="__tabbed_1_6" name="__tabbed_1" type="radio" /><input id="__tabbed_1_7" name="__tabbed_1" type="radio" /><input id="__tabbed_1_8" name="__tabbed_1" type="radio" /><input id="__tabbed_1_9" name="__tabbed_1" type="radio" /><input id="__tabbed_1_10" name="__tabbed_1" type="radio" /><input id="__tabbed_1_11" name="__tabbed_1" type="radio" /><input id="__tabbed_1_12" name="__tabbed_1" type="radio" /><div class="tabbed-labels"><label for="__tabbed_1_1">Python</label><label for="__tabbed_1_2">C++</label><label for="__tabbed_1_3">Java</label><label for="__tabbed_1_4">C#</label><label for="__tabbed_1_5">Go</label><label for="__tabbed_1_6">Swift</label><label for="__tabbed_1_7">JS</label><label for="__tabbed_1_8">TS</label><label for="__tabbed_1_9">Dart</label><label for="__tabbed_1_10">Rust</label><label for="__tabbed_1_11">C</label><label for="__tabbed_1_12">Zig</label></div>
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<p>“节点高度”是指从该节点到其最远叶节点的距离,即所经过的“边”的数量。需要特别注意的是,叶节点的高度为 0 ,而空节点的高度为 -1 。我们将创建两个工具函数,分别用于获取和更新节点的高度</p>
<p>“节点高度”是指从该节点到其最远叶节点的距离,即所经过的“边”的数量。需要特别注意的是,叶节点的高度为 <span class="arithmatex">\(0\)</span> ,而空节点的高度为 <span class="arithmatex">\(-1\)</span> 。我们将创建两个工具函数,分别用于获取和更新节点的高度</p>
<div class="tabbed-set tabbed-alternate" data-tabs="2:12"><input checked="checked" id="__tabbed_2_1" name="__tabbed_2" type="radio" /><input id="__tabbed_2_2" name="__tabbed_2" type="radio" /><input id="__tabbed_2_3" name="__tabbed_2" type="radio" /><input id="__tabbed_2_4" name="__tabbed_2" type="radio" /><input id="__tabbed_2_5" name="__tabbed_2" type="radio" /><input id="__tabbed_2_6" name="__tabbed_2" type="radio" /><input id="__tabbed_2_7" name="__tabbed_2" type="radio" /><input id="__tabbed_2_8" name="__tabbed_2" type="radio" /><input id="__tabbed_2_9" name="__tabbed_2" type="radio" /><input id="__tabbed_2_10" name="__tabbed_2" type="radio" /><input id="__tabbed_2_11" name="__tabbed_2" type="radio" /><input id="__tabbed_2_12" name="__tabbed_2" type="radio" /><div class="tabbed-labels"><label for="__tabbed_2_1">Python</label><label for="__tabbed_2_2">C++</label><label for="__tabbed_2_3">Java</label><label for="__tabbed_2_4">C#</label><label for="__tabbed_2_5">Go</label><label for="__tabbed_2_6">Swift</label><label for="__tabbed_2_7">JS</label><label for="__tabbed_2_8">TS</label><label for="__tabbed_2_9">Dart</label><label for="__tabbed_2_10">Rust</label><label for="__tabbed_2_11">C</label><label for="__tabbed_2_12">Zig</label></div>
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<h3 id="2">2. &nbsp; 节点平衡因子<a class="headerlink" href="#2" title="Permanent link">&para;</a></h3>
<p>节点的「平衡因子 balance factor」定义为节点左子树的高度减去右子树的高度,同时规定空节点的平衡因子为 0 。我们同样将获取节点平衡因子的功能封装成函数,方便后续使用</p>
<p>节点的「平衡因子 balance factor」定义为节点左子树的高度减去右子树的高度,同时规定空节点的平衡因子为 <span class="arithmatex">\(0\)</span> 。我们同样将获取节点平衡因子的功能封装成函数,方便后续使用</p>
<div class="tabbed-set tabbed-alternate" data-tabs="3:12"><input checked="checked" id="__tabbed_3_1" name="__tabbed_3" type="radio" /><input id="__tabbed_3_2" name="__tabbed_3" type="radio" /><input id="__tabbed_3_3" name="__tabbed_3" type="radio" /><input id="__tabbed_3_4" name="__tabbed_3" type="radio" /><input id="__tabbed_3_5" name="__tabbed_3" type="radio" /><input id="__tabbed_3_6" name="__tabbed_3" type="radio" /><input id="__tabbed_3_7" name="__tabbed_3" type="radio" /><input id="__tabbed_3_8" name="__tabbed_3" type="radio" /><input id="__tabbed_3_9" name="__tabbed_3" type="radio" /><input id="__tabbed_3_10" name="__tabbed_3" type="radio" /><input id="__tabbed_3_11" name="__tabbed_3" type="radio" /><input id="__tabbed_3_12" name="__tabbed_3" type="radio" /><div class="tabbed-labels"><label for="__tabbed_3_1">Python</label><label for="__tabbed_3_2">C++</label><label for="__tabbed_3_3">Java</label><label for="__tabbed_3_4">C#</label><label for="__tabbed_3_5">Go</label><label for="__tabbed_3_6">Swift</label><label for="__tabbed_3_7">JS</label><label for="__tabbed_3_8">TS</label><label for="__tabbed_3_9">Dart</label><label for="__tabbed_3_10">Rust</label><label for="__tabbed_3_11">C</label><label for="__tabbed_3_12">Zig</label></div>
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@@ -4109,9 +4109,9 @@
</div>
<h2 id="752-avl">7.5.2 &nbsp; AVL 树旋转<a class="headerlink" href="#752-avl" title="Permanent link">&para;</a></h2>
<p>AVL 树的特点在于“旋转”操作,它能够在不影响二叉树的中序遍历序列的前提下,使失衡节点重新恢复平衡。换句话说,<strong>旋转操作既能保持“二叉搜索树”的性质,也能使树重新变为“平衡二叉树”</strong></p>
<p>我们将平衡因子绝对值 <span class="arithmatex">\(&gt; 1\)</span> 的节点称为“失衡节点”。根据节点失衡情况的不同,旋转操作分为四种:右旋、左旋、先右旋后左旋、先左旋后右旋。下面我们将详细介绍这些旋转操作。</p>
<p>我们将平衡因子绝对值 <span class="arithmatex">\(&gt; 1\)</span> 的节点称为“失衡节点”。根据节点失衡情况的不同,旋转操作分为四种:右旋、左旋、先右旋后左旋、先左旋后右旋。下面详细介绍这些旋转操作。</p>
<h3 id="1_1">1. &nbsp; 右旋<a class="headerlink" href="#1_1" title="Permanent link">&para;</a></h3>
<p>如图 7-26 所示,节点下方为平衡因子。从底至顶看,二叉树中首个失衡节点是“节点 3”。我们关注以该失衡节点为根节点的子树,将该节点记为 <code>node</code> ,其左子节点记为 <code>child</code> ,执行“右旋”操作。完成右旋后,子树已经恢复平衡,并且仍然保持二叉搜索树的性。</p>
<p>如图 7-26 所示,节点下方为平衡因子。从底至顶看,二叉树中首个失衡节点是“节点 3”。我们关注以该失衡节点为根节点的子树,将该节点记为 <code>node</code> ,其左子节点记为 <code>child</code> ,执行“右旋”操作。完成右旋后,子树恢复平衡,并且仍然保持二叉搜索树的性</p>
<div class="tabbed-set tabbed-alternate" data-tabs="4:4"><input checked="checked" id="__tabbed_4_1" name="__tabbed_4" type="radio" /><input id="__tabbed_4_2" name="__tabbed_4" type="radio" /><input id="__tabbed_4_3" name="__tabbed_4" type="radio" /><input id="__tabbed_4_4" name="__tabbed_4" type="radio" /><div class="tabbed-labels"><label for="__tabbed_4_1">&lt;1&gt;</label><label for="__tabbed_4_2">&lt;2&gt;</label><label for="__tabbed_4_3">&lt;3&gt;</label><label for="__tabbed_4_4">&lt;4&gt;</label></div>
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@@ -4134,7 +4134,7 @@
<p><a class="glightbox" href="../avl_tree.assets/avltree_right_rotate_with_grandchild.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="有 grandChild 的右旋操作" class="animation-figure" src="../avl_tree.assets/avltree_right_rotate_with_grandchild.png" /></a></p>
<p align="center"> 图 7-27 &nbsp; 有 grandChild 的右旋操作 </p>
<p>“向右旋转”是一种形象化的说法,实际上需要通过修改节点指针来实现,代码如下所示</p>
<p>“向右旋转”是一种形象化的说法,实际上需要通过修改节点指针来实现,代码如下所示</p>
<div class="tabbed-set tabbed-alternate" data-tabs="5:12"><input checked="checked" id="__tabbed_5_1" name="__tabbed_5" type="radio" /><input id="__tabbed_5_2" name="__tabbed_5" type="radio" /><input id="__tabbed_5_3" name="__tabbed_5" type="radio" /><input id="__tabbed_5_4" name="__tabbed_5" type="radio" /><input id="__tabbed_5_5" name="__tabbed_5" type="radio" /><input id="__tabbed_5_6" name="__tabbed_5" type="radio" /><input id="__tabbed_5_7" name="__tabbed_5" type="radio" /><input id="__tabbed_5_8" name="__tabbed_5" type="radio" /><input id="__tabbed_5_9" name="__tabbed_5" type="radio" /><input id="__tabbed_5_10" name="__tabbed_5" type="radio" /><input id="__tabbed_5_11" name="__tabbed_5" type="radio" /><input id="__tabbed_5_12" name="__tabbed_5" type="radio" /><div class="tabbed-labels"><label for="__tabbed_5_1">Python</label><label for="__tabbed_5_2">C++</label><label for="__tabbed_5_3">Java</label><label for="__tabbed_5_4">C#</label><label for="__tabbed_5_5">Go</label><label for="__tabbed_5_6">Swift</label><label for="__tabbed_5_7">JS</label><label for="__tabbed_5_8">TS</label><label for="__tabbed_5_9">Dart</label><label for="__tabbed_5_10">Rust</label><label for="__tabbed_5_11">C</label><label for="__tabbed_5_12">Zig</label></div>
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<h3 id="2_1">2. &nbsp; 左旋<a class="headerlink" href="#2_1" title="Permanent link">&para;</a></h3>
<p>相应,如果考虑上述失衡二叉树的“镜像”,则需要执行图 7-28 所示的“左旋”操作。</p>
<p>相应,如果考虑上述失衡二叉树的“镜像”,则需要执行图 7-28 所示的“左旋”操作。</p>
<p><a class="glightbox" href="../avl_tree.assets/avltree_left_rotate.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="左旋操作" class="animation-figure" src="../avl_tree.assets/avltree_left_rotate.png" /></a></p>
<p align="center"> 图 7-28 &nbsp; 左旋操作 </p>
@@ -4345,7 +4345,7 @@
<p><a class="glightbox" href="../avl_tree.assets/avltree_left_rotate_with_grandchild.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="有 grandChild 的左旋操作" class="animation-figure" src="../avl_tree.assets/avltree_left_rotate_with_grandchild.png" /></a></p>
<p align="center"> 图 7-29 &nbsp; 有 grandChild 的左旋操作 </p>
<p>可以观察到,<strong>右旋和左旋操作在逻辑上是镜像对称的,它们分别解决的两种失衡情况也是对称的</strong>。基于对称性,我们只需将右旋的实现代码中的所有的 <code>left</code> 替换为 <code>right</code> ,将所有的 <code>right</code> 替换为 <code>left</code> ,即可得到左旋的实现代码</p>
<p>可以观察到,<strong>右旋和左旋操作在逻辑上是镜像对称的,它们分别解决的两种失衡情况也是对称的</strong>。基于对称性,我们只需将右旋的实现代码中的所有的 <code>left</code> 替换为 <code>right</code> ,将所有的 <code>right</code> 替换为 <code>left</code> ,即可得到左旋的实现代码</p>
<div class="tabbed-set tabbed-alternate" data-tabs="6:12"><input checked="checked" id="__tabbed_6_1" name="__tabbed_6" type="radio" /><input id="__tabbed_6_2" name="__tabbed_6" type="radio" /><input id="__tabbed_6_3" name="__tabbed_6" type="radio" /><input id="__tabbed_6_4" name="__tabbed_6" type="radio" /><input id="__tabbed_6_5" name="__tabbed_6" type="radio" /><input id="__tabbed_6_6" name="__tabbed_6" type="radio" /><input id="__tabbed_6_7" name="__tabbed_6" type="radio" /><input id="__tabbed_6_8" name="__tabbed_6" type="radio" /><input id="__tabbed_6_9" name="__tabbed_6" type="radio" /><input id="__tabbed_6_10" name="__tabbed_6" type="radio" /><input id="__tabbed_6_11" name="__tabbed_6" type="radio" /><input id="__tabbed_6_12" name="__tabbed_6" type="radio" /><div class="tabbed-labels"><label for="__tabbed_6_1">Python</label><label for="__tabbed_6_2">C++</label><label for="__tabbed_6_3">Java</label><label for="__tabbed_6_4">C#</label><label for="__tabbed_6_5">Go</label><label for="__tabbed_6_6">Swift</label><label for="__tabbed_6_7">JS</label><label for="__tabbed_6_8">TS</label><label for="__tabbed_6_9">Dart</label><label for="__tabbed_6_10">Rust</label><label for="__tabbed_6_11">C</label><label for="__tabbed_6_12">Zig</label></div>
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<p align="center"> 图 7-30 &nbsp; 先左旋后右旋 </p>
<h3 id="4">4. &nbsp; 先右旋后左旋<a class="headerlink" href="#4" title="Permanent link">&para;</a></h3>
<p>如图 7-31 所示,对于上述失衡二叉树的镜像情况,需要先对 <code>child</code> 执行“右旋”,然后<code>node</code> 执行“左旋”。</p>
<p>如图 7-31 所示,对于上述失衡二叉树的镜像情况,需要先对 <code>child</code> 执行“右旋”,<code>node</code> 执行“左旋”。</p>
<p><a class="glightbox" href="../avl_tree.assets/avltree_right_left_rotate.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="先右旋后左旋" class="animation-figure" src="../avl_tree.assets/avltree_right_left_rotate.png" /></a></p>
<p align="center"> 图 7-31 &nbsp; 先右旋后左旋 </p>
<h3 id="5">5. &nbsp; 旋转的选择<a class="headerlink" href="#5" title="Permanent link">&para;</a></h3>
<p>图 7-32 展示的四种失衡情况与上述案例逐个对应,分别需要采用右旋、左旋、先右后左、先左后右的旋转操作。</p>
<p>图 7-32 展示的四种失衡情况与上述案例逐个对应,分别需要采用右旋、左旋后右旋、先右后左旋、左旋的操作。</p>
<p><a class="glightbox" href="../avl_tree.assets/avltree_rotation_cases.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="AVL 树的四种旋转情况" class="animation-figure" src="../avl_tree.assets/avltree_rotation_cases.png" /></a></p>
<p align="center"> 图 7-32 &nbsp; AVL 树的四种旋转情况 </p>
@@ -4576,29 +4576,29 @@
</thead>
<tbody>
<tr>
<td><span class="arithmatex">\(&gt; 1\)</span> 左偏树)</td>
<td><span class="arithmatex">\(&gt; 1\)</span> (左偏树)</td>
<td><span class="arithmatex">\(\geq 0\)</span></td>
<td>右旋</td>
</tr>
<tr>
<td><span class="arithmatex">\(&gt; 1\)</span> 左偏树)</td>
<td><span class="arithmatex">\(&gt; 1\)</span> (左偏树)</td>
<td><span class="arithmatex">\(&lt;0\)</span></td>
<td>先左旋后右旋</td>
</tr>
<tr>
<td><span class="arithmatex">\(&lt; -1\)</span> 右偏树)</td>
<td><span class="arithmatex">\(&lt; -1\)</span> (右偏树)</td>
<td><span class="arithmatex">\(\leq 0\)</span></td>
<td>左旋</td>
</tr>
<tr>
<td><span class="arithmatex">\(&lt; -1\)</span> 右偏树)</td>
<td><span class="arithmatex">\(&lt; -1\)</span> (右偏树)</td>
<td><span class="arithmatex">\(&gt;0\)</span></td>
<td>先右旋后左旋</td>
</tr>
</tbody>
</table>
</div>
<p>为了便于使用,我们将旋转操作封装成一个函数。<strong>有了这个函数,我们就能对各种失衡情况进行旋转,使失衡节点重新恢复平衡</strong></p>
<p>为了便于使用,我们将旋转操作封装成一个函数。<strong>有了这个函数,我们就能对各种失衡情况进行旋转,使失衡节点重新恢复平衡</strong>代码如下所示:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="7:12"><input checked="checked" id="__tabbed_7_1" name="__tabbed_7" type="radio" /><input id="__tabbed_7_2" name="__tabbed_7" type="radio" /><input id="__tabbed_7_3" name="__tabbed_7" type="radio" /><input id="__tabbed_7_4" name="__tabbed_7" type="radio" /><input id="__tabbed_7_5" name="__tabbed_7" type="radio" /><input id="__tabbed_7_6" name="__tabbed_7" type="radio" /><input id="__tabbed_7_7" name="__tabbed_7" type="radio" /><input id="__tabbed_7_8" name="__tabbed_7" type="radio" /><input id="__tabbed_7_9" name="__tabbed_7" type="radio" /><input id="__tabbed_7_10" name="__tabbed_7" type="radio" /><input id="__tabbed_7_11" name="__tabbed_7" type="radio" /><input id="__tabbed_7_12" name="__tabbed_7" type="radio" /><div class="tabbed-labels"><label for="__tabbed_7_1">Python</label><label for="__tabbed_7_2">C++</label><label for="__tabbed_7_3">Java</label><label for="__tabbed_7_4">C#</label><label for="__tabbed_7_5">Go</label><label for="__tabbed_7_6">Swift</label><label for="__tabbed_7_7">JS</label><label for="__tabbed_7_8">TS</label><label for="__tabbed_7_9">Dart</label><label for="__tabbed_7_10">Rust</label><label for="__tabbed_7_11">C</label><label for="__tabbed_7_12">Zig</label></div>
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<h2 id="753-avl">7.5.3 &nbsp; AVL 树常用操作<a class="headerlink" href="#753-avl" title="Permanent link">&para;</a></h2>
<h3 id="1_2">1. &nbsp; 插入节点<a class="headerlink" href="#1_2" title="Permanent link">&para;</a></h3>
<p>AVL 树的节点插入操作与二叉搜索树在主体上类似。唯一的区别在于,在 AVL 树中插入节点后,从该节点到根节点的路径上可能会出现一系列失衡节点。因此,<strong>我们需要从这个节点开始,自底向上执行旋转操作,使所有失衡节点恢复平衡</strong></p>
<p>AVL 树的节点插入操作与二叉搜索树在主体上类似。唯一的区别在于,在 AVL 树中插入节点后,从该节点到根节点的路径上可能会出现一系列失衡节点。因此,<strong>我们需要从这个节点开始,自底向上执行旋转操作,使所有失衡节点恢复平衡</strong>代码如下所示:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="8:12"><input checked="checked" id="__tabbed_8_1" name="__tabbed_8" type="radio" /><input id="__tabbed_8_2" name="__tabbed_8" type="radio" /><input id="__tabbed_8_3" name="__tabbed_8" type="radio" /><input id="__tabbed_8_4" name="__tabbed_8" type="radio" /><input id="__tabbed_8_5" name="__tabbed_8" type="radio" /><input id="__tabbed_8_6" name="__tabbed_8" type="radio" /><input id="__tabbed_8_7" name="__tabbed_8" type="radio" /><input id="__tabbed_8_8" name="__tabbed_8" type="radio" /><input id="__tabbed_8_9" name="__tabbed_8" type="radio" /><input id="__tabbed_8_10" name="__tabbed_8" type="radio" /><input id="__tabbed_8_11" name="__tabbed_8" type="radio" /><input id="__tabbed_8_12" name="__tabbed_8" type="radio" /><div class="tabbed-labels"><label for="__tabbed_8_1">Python</label><label for="__tabbed_8_2">C++</label><label for="__tabbed_8_3">Java</label><label for="__tabbed_8_4">C#</label><label for="__tabbed_8_5">Go</label><label for="__tabbed_8_6">Swift</label><label for="__tabbed_8_7">JS</label><label for="__tabbed_8_8">TS</label><label for="__tabbed_8_9">Dart</label><label for="__tabbed_8_10">Rust</label><label for="__tabbed_8_11">C</label><label for="__tabbed_8_12">Zig</label></div>
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<h3 id="2_2">2. &nbsp; 删除节点<a class="headerlink" href="#2_2" title="Permanent link">&para;</a></h3>
<p>类似地,在二叉搜索树的删除节点方法的基础上,需要从底至顶执行旋转操作,使所有失衡节点恢复平衡。</p>
<p>类似地,在二叉搜索树的删除节点方法的基础上,需要从底至顶执行旋转操作,使所有失衡节点恢复平衡。代码如下所示:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="9:12"><input checked="checked" id="__tabbed_9_1" name="__tabbed_9" type="radio" /><input id="__tabbed_9_2" name="__tabbed_9" type="radio" /><input id="__tabbed_9_3" name="__tabbed_9" type="radio" /><input id="__tabbed_9_4" name="__tabbed_9" type="radio" /><input id="__tabbed_9_5" name="__tabbed_9" type="radio" /><input id="__tabbed_9_6" name="__tabbed_9" type="radio" /><input id="__tabbed_9_7" name="__tabbed_9" type="radio" /><input id="__tabbed_9_8" name="__tabbed_9" type="radio" /><input id="__tabbed_9_9" name="__tabbed_9" type="radio" /><input id="__tabbed_9_10" name="__tabbed_9" type="radio" /><input id="__tabbed_9_11" name="__tabbed_9" type="radio" /><input id="__tabbed_9_12" name="__tabbed_9" type="radio" /><div class="tabbed-labels"><label for="__tabbed_9_1">Python</label><label for="__tabbed_9_2">C++</label><label for="__tabbed_9_3">Java</label><label for="__tabbed_9_4">C#</label><label for="__tabbed_9_5">Go</label><label for="__tabbed_9_6">Swift</label><label for="__tabbed_9_7">JS</label><label for="__tabbed_9_8">TS</label><label for="__tabbed_9_9">Dart</label><label for="__tabbed_9_10">Rust</label><label for="__tabbed_9_11">C</label><label for="__tabbed_9_12">Zig</label></div>
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<p align="center"> 图 7-17 &nbsp; 二叉搜索树查找节点示例 </p>
<p>二叉搜索树的查找操作与二分查找算法的工作原理一致,都是每轮排除一半情况。循环次数最多为二叉树的高度,当二叉树平衡时,使用 <span class="arithmatex">\(O(\log n)\)</span> 时间。</p>
<p>二叉搜索树的查找操作与二分查找算法的工作原理一致,都是每轮排除一半情况。循环次数最多为二叉树的高度,当二叉树平衡时,使用 <span class="arithmatex">\(O(\log n)\)</span> 时间。示例代码如下:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="2:12"><input checked="checked" id="__tabbed_2_1" name="__tabbed_2" type="radio" /><input id="__tabbed_2_2" name="__tabbed_2" type="radio" /><input id="__tabbed_2_3" name="__tabbed_2" type="radio" /><input id="__tabbed_2_4" name="__tabbed_2" type="radio" /><input id="__tabbed_2_5" name="__tabbed_2" type="radio" /><input id="__tabbed_2_6" name="__tabbed_2" type="radio" /><input id="__tabbed_2_7" name="__tabbed_2" type="radio" /><input id="__tabbed_2_8" name="__tabbed_2" type="radio" /><input id="__tabbed_2_9" name="__tabbed_2" type="radio" /><input id="__tabbed_2_10" name="__tabbed_2" type="radio" /><input id="__tabbed_2_11" name="__tabbed_2" type="radio" /><input id="__tabbed_2_12" name="__tabbed_2" type="radio" /><div class="tabbed-labels"><label for="__tabbed_2_1">Python</label><label for="__tabbed_2_2">C++</label><label for="__tabbed_2_3">Java</label><label for="__tabbed_2_4">C#</label><label for="__tabbed_2_5">Go</label><label for="__tabbed_2_6">Swift</label><label for="__tabbed_2_7">JS</label><label for="__tabbed_2_8">TS</label><label for="__tabbed_2_9">Dart</label><label for="__tabbed_2_10">Rust</label><label for="__tabbed_2_11">C</label><label for="__tabbed_2_12">Zig</label></div>
<div class="tabbed-content">
<div class="tabbed-block">
@@ -4160,9 +4160,9 @@
</div>
<p>与查找节点相同,插入节点使用 <span class="arithmatex">\(O(\log n)\)</span> 时间。</p>
<h3 id="3">3. &nbsp; 删除节点<a class="headerlink" href="#3" title="Permanent link">&para;</a></h3>
<p>先在二叉树中查找到目标节点,再将其从二叉树中删除。</p>
<p>先在二叉树中查找到目标节点,再将其删除。</p>
<p>与插入节点类似,我们需要保证在删除操作完成后,二叉搜索树的“左子树 &lt; 根节点 &lt; 右子树”的性质仍然满足。</p>
<p>因此,我们需要根据目标节点的子节点数量,共分为 0、1 和 2 三种情况,执行对应的删除节点操作。</p>
<p>因此,我们根据目标节点的子节点数量, 0、1 和 2 三种情况,执行对应的删除节点操作。</p>
<p>如图 7-19 所示,当待删除节点的度为 <span class="arithmatex">\(0\)</span> 时,表示该节点是叶节点,可以直接删除。</p>
<p><a class="glightbox" href="../binary_search_tree.assets/bst_remove_case1.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="在二叉搜索树中删除节点(度为 0 )" class="animation-figure" src="../binary_search_tree.assets/bst_remove_case1.png" /></a></p>
<p align="center"> 图 7-19 &nbsp; 在二叉搜索树中删除节点(度为 0 ) </p>
@@ -4171,11 +4171,11 @@
<p><a class="glightbox" href="../binary_search_tree.assets/bst_remove_case2.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="在二叉搜索树中删除节点(度为 1 )" class="animation-figure" src="../binary_search_tree.assets/bst_remove_case2.png" /></a></p>
<p align="center"> 图 7-20 &nbsp; 在二叉搜索树中删除节点(度为 1 ) </p>
<p>当待删除节点的度为 <span class="arithmatex">\(2\)</span> 时,我们无法直接删除它,而需要使用一个节点替换该节点。由于要保持二叉搜索树“左 <span class="arithmatex">\(&lt;\)</span><span class="arithmatex">\(&lt;\)</span> 右”的性质,<strong>因此这个节点可以是右子树的最小节点或左子树的最大节点</strong></p>
<p>假设我们选择右子树的最小节点(中序遍历的下一个节点),则删除操作流程如图 7-21 所示。</p>
<p>当待删除节点的度为 <span class="arithmatex">\(2\)</span> 时,我们无法直接删除它,而需要使用一个节点替换该节点。由于要保持二叉搜索树“左子树 <span class="arithmatex">\(&lt;\)</span>节点 <span class="arithmatex">\(&lt;\)</span>子树”的性质,<strong>因此这个节点可以是右子树的最小节点或左子树的最大节点</strong></p>
<p>假设我们选择右子树的最小节点(中序遍历的下一个节点),则删除操作流程如图 7-21 所示。</p>
<ol>
<li>找到待删除节点在“中序遍历序列”中的下一个节点,记为 <code>tmp</code></li>
<li> <code>tmp</code> 的值覆盖待删除节点的值,并在树中递归删除节点 <code>tmp</code></li>
<li> <code>tmp</code> 的值覆盖待删除节点的值,并在树中递归删除节点 <code>tmp</code></li>
</ol>
<div class="tabbed-set tabbed-alternate" data-tabs="4:4"><input checked="checked" id="__tabbed_4_1" name="__tabbed_4" type="radio" /><input id="__tabbed_4_2" name="__tabbed_4" type="radio" /><input id="__tabbed_4_3" name="__tabbed_4" type="radio" /><input id="__tabbed_4_4" name="__tabbed_4" type="radio" /><div class="tabbed-labels"><label for="__tabbed_4_1">&lt;1&gt;</label><label for="__tabbed_4_2">&lt;2&gt;</label><label for="__tabbed_4_3">&lt;3&gt;</label><label for="__tabbed_4_4">&lt;4&gt;</label></div>
<div class="tabbed-content">
@@ -4195,7 +4195,7 @@
</div>
<p align="center"> 图 7-21 &nbsp; 在二叉搜索树中删除节点(度为 2 ) </p>
<p>删除节点操作同样使用 <span class="arithmatex">\(O(\log n)\)</span> 时间,其中查找待删除节点需要 <span class="arithmatex">\(O(\log n)\)</span> 时间,获取中序遍历后继节点需要 <span class="arithmatex">\(O(\log n)\)</span> 时间。</p>
<p>删除节点操作同样使用 <span class="arithmatex">\(O(\log n)\)</span> 时间,其中查找待删除节点需要 <span class="arithmatex">\(O(\log n)\)</span> 时间,获取中序遍历后继节点需要 <span class="arithmatex">\(O(\log n)\)</span> 时间。示例代码如下:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="5:12"><input checked="checked" id="__tabbed_5_1" name="__tabbed_5" type="radio" /><input id="__tabbed_5_2" name="__tabbed_5" type="radio" /><input id="__tabbed_5_3" name="__tabbed_5" type="radio" /><input id="__tabbed_5_4" name="__tabbed_5" type="radio" /><input id="__tabbed_5_5" name="__tabbed_5" type="radio" /><input id="__tabbed_5_6" name="__tabbed_5" type="radio" /><input id="__tabbed_5_7" name="__tabbed_5" type="radio" /><input id="__tabbed_5_8" name="__tabbed_5" type="radio" /><input id="__tabbed_5_9" name="__tabbed_5" type="radio" /><input id="__tabbed_5_10" name="__tabbed_5" type="radio" /><input id="__tabbed_5_11" name="__tabbed_5" type="radio" /><input id="__tabbed_5_12" name="__tabbed_5" type="radio" /><div class="tabbed-labels"><label for="__tabbed_5_1">Python</label><label for="__tabbed_5_2">C++</label><label for="__tabbed_5_3">Java</label><label for="__tabbed_5_4">C#</label><label for="__tabbed_5_5">Go</label><label for="__tabbed_5_6">Swift</label><label for="__tabbed_5_7">JS</label><label for="__tabbed_5_8">TS</label><label for="__tabbed_5_9">Dart</label><label for="__tabbed_5_10">Rust</label><label for="__tabbed_5_11">C</label><label for="__tabbed_5_12">Zig</label></div>
<div class="tabbed-content">
<div class="tabbed-block">
@@ -4854,7 +4854,7 @@
<p align="center"> 图 7-22 &nbsp; 二叉搜索树的中序遍历序列 </p>
<h2 id="742">7.4.2 &nbsp; 二叉搜索树的效率<a class="headerlink" href="#742" title="Permanent link">&para;</a></h2>
<p>给定一组数据,我们考虑使用数组或二叉搜索树存储。观察表 7-2 ,二叉搜索树的各项操作的时间复杂度都是对数阶,具有稳定且高效的性能表现。只有在高频添加、低频查找删除数据适用场景下,数组比二叉搜索树的效率更高。</p>
<p>给定一组数据,我们考虑使用数组或二叉搜索树存储。观察表 7-2 ,二叉搜索树的各项操作的时间复杂度都是对数阶,具有稳定且高效的性能。只有在高频添加、低频查找删除数据场景下,数组比二叉搜索树的效率更高。</p>
<p align="center"> 表 7-2 &nbsp; 数组与搜索树的效率对比 </p>
<div class="center-table">
@@ -4887,8 +4887,8 @@
</div>
<p>在理想情况下,二叉搜索树是“平衡”的,这样就可以在 <span class="arithmatex">\(\log n\)</span> 轮循环内查找任意节点。</p>
<p>然而,如果我们在二叉搜索树中不断地插入和删除节点,可能导致二叉树退化为图 7-23 所示的链表,这时各种操作的时间复杂度也会退化为 <span class="arithmatex">\(O(n)\)</span></p>
<p><a class="glightbox" href="../binary_search_tree.assets/bst_degradation.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉搜索树退化" class="animation-figure" src="../binary_search_tree.assets/bst_degradation.png" /></a></p>
<p align="center"> 图 7-23 &nbsp; 二叉搜索树退化 </p>
<p><a class="glightbox" href="../binary_search_tree.assets/bst_degradation.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉搜索树退化" class="animation-figure" src="../binary_search_tree.assets/bst_degradation.png" /></a></p>
<p align="center"> 图 7-23 &nbsp; 二叉搜索树退化 </p>
<h2 id="743">7.4.3 &nbsp; 二叉搜索树常见应用<a class="headerlink" href="#743" title="Permanent link">&para;</a></h2>
<ul>
+23 -23
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@@ -3518,7 +3518,7 @@
<!-- Page content -->
<h1 id="71">7.1 &nbsp; 二叉树<a class="headerlink" href="#71" title="Permanent link">&para;</a></h1>
<p>「二叉树 binary tree」是一种非线性数据结构,代表祖先后代之间的派生关系,体现“一分为二”的分治逻辑。与链表类似,二叉树的基本单元是节点,每个节点包含值、左子节点引用右子节点引用。</p>
<p>「二叉树 binary tree」是一种非线性数据结构,代表祖先”与“后代之间的派生关系,体现“一分为二”的分治逻辑。与链表类似,二叉树的基本单元是节点,每个节点包含值、左子节点引用右子节点引用。</p>
<div class="tabbed-set tabbed-alternate" data-tabs="1:12"><input checked="checked" id="__tabbed_1_1" name="__tabbed_1" type="radio" /><input id="__tabbed_1_2" name="__tabbed_1" type="radio" /><input id="__tabbed_1_3" name="__tabbed_1" type="radio" /><input id="__tabbed_1_4" name="__tabbed_1" type="radio" /><input id="__tabbed_1_5" name="__tabbed_1" type="radio" /><input id="__tabbed_1_6" name="__tabbed_1" type="radio" /><input id="__tabbed_1_7" name="__tabbed_1" type="radio" /><input id="__tabbed_1_8" name="__tabbed_1" type="radio" /><input id="__tabbed_1_9" name="__tabbed_1" type="radio" /><input id="__tabbed_1_10" name="__tabbed_1" type="radio" /><input id="__tabbed_1_11" name="__tabbed_1" type="radio" /><input id="__tabbed_1_12" name="__tabbed_1" type="radio" /><div class="tabbed-labels"><label for="__tabbed_1_1">Python</label><label for="__tabbed_1_2">C++</label><label for="__tabbed_1_3">Java</label><label for="__tabbed_1_4">C#</label><label for="__tabbed_1_5">Go</label><label for="__tabbed_1_6">Swift</label><label for="__tabbed_1_7">JS</label><label for="__tabbed_1_8">TS</label><label for="__tabbed_1_9">Dart</label><label for="__tabbed_1_10">Rust</label><label for="__tabbed_1_11">C</label><label for="__tabbed_1_12">Zig</label></div>
<div class="tabbed-content">
<div class="tabbed-block">
@@ -3701,7 +3701,7 @@
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>请注意,我们通常将“高度”和“深度”定义为“走过边的数量”,但有些题目或教材可能会将其定义为“走过节点的数量”。在这种情况下,高度和深度都需要加 1 。</p>
<p>请注意,我们通常将“高度”和“深度”定义为“经过的边的数量”,但有些题目或教材可能会将其定义为“经过的节点的数量”。在这种情况下,高度和深度都需要加 1 。</p>
</div>
<h2 id="712">7.1.2 &nbsp; 二叉树基本操作<a class="headerlink" href="#712" title="Permanent link">&para;</a></h2>
<h3 id="1">1. &nbsp; 初始化二叉树<a class="headerlink" href="#1" title="Permanent link">&para;</a></h3>
@@ -3716,7 +3716,7 @@
<a id="__codelineno-12-5" name="__codelineno-12-5" href="#__codelineno-12-5"></a><span class="n">n3</span> <span class="o">=</span> <span class="n">TreeNode</span><span class="p">(</span><span class="n">val</span><span class="o">=</span><span class="mi">3</span><span class="p">)</span>
<a id="__codelineno-12-6" name="__codelineno-12-6" href="#__codelineno-12-6"></a><span class="n">n4</span> <span class="o">=</span> <span class="n">TreeNode</span><span class="p">(</span><span class="n">val</span><span class="o">=</span><span class="mi">4</span><span class="p">)</span>
<a id="__codelineno-12-7" name="__codelineno-12-7" href="#__codelineno-12-7"></a><span class="n">n5</span> <span class="o">=</span> <span class="n">TreeNode</span><span class="p">(</span><span class="n">val</span><span class="o">=</span><span class="mi">5</span><span class="p">)</span>
<a id="__codelineno-12-8" name="__codelineno-12-8" href="#__codelineno-12-8"></a><span class="c1"># 构建引用指向(即指针)</span>
<a id="__codelineno-12-8" name="__codelineno-12-8" href="#__codelineno-12-8"></a><span class="c1"># 构建节点之间的引用(指针)</span>
<a id="__codelineno-12-9" name="__codelineno-12-9" href="#__codelineno-12-9"></a><span class="n">n1</span><span class="o">.</span><span class="n">left</span> <span class="o">=</span> <span class="n">n2</span>
<a id="__codelineno-12-10" name="__codelineno-12-10" href="#__codelineno-12-10"></a><span class="n">n1</span><span class="o">.</span><span class="n">right</span> <span class="o">=</span> <span class="n">n3</span>
<a id="__codelineno-12-11" name="__codelineno-12-11" href="#__codelineno-12-11"></a><span class="n">n2</span><span class="o">.</span><span class="n">left</span> <span class="o">=</span> <span class="n">n4</span>
@@ -3731,7 +3731,7 @@
<a id="__codelineno-13-5" name="__codelineno-13-5" href="#__codelineno-13-5"></a><span class="n">TreeNode</span><span class="o">*</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span>
<a id="__codelineno-13-6" name="__codelineno-13-6" href="#__codelineno-13-6"></a><span class="n">TreeNode</span><span class="o">*</span><span class="w"> </span><span class="n">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="mi">4</span><span class="p">);</span>
<a id="__codelineno-13-7" name="__codelineno-13-7" href="#__codelineno-13-7"></a><span class="n">TreeNode</span><span class="o">*</span><span class="w"> </span><span class="n">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
<a id="__codelineno-13-8" name="__codelineno-13-8" href="#__codelineno-13-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-13-8" name="__codelineno-13-8" href="#__codelineno-13-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-13-9" name="__codelineno-13-9" href="#__codelineno-13-9"></a><span class="n">n1</span><span class="o">-&gt;</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n2</span><span class="p">;</span>
<a id="__codelineno-13-10" name="__codelineno-13-10" href="#__codelineno-13-10"></a><span class="n">n1</span><span class="o">-&gt;</span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n3</span><span class="p">;</span>
<a id="__codelineno-13-11" name="__codelineno-13-11" href="#__codelineno-13-11"></a><span class="n">n2</span><span class="o">-&gt;</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n4</span><span class="p">;</span>
@@ -3745,7 +3745,7 @@
<a id="__codelineno-14-4" name="__codelineno-14-4" href="#__codelineno-14-4"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span>
<a id="__codelineno-14-5" name="__codelineno-14-5" href="#__codelineno-14-5"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="mi">4</span><span class="p">);</span>
<a id="__codelineno-14-6" name="__codelineno-14-6" href="#__codelineno-14-6"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
<a id="__codelineno-14-7" name="__codelineno-14-7" href="#__codelineno-14-7"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-14-7" name="__codelineno-14-7" href="#__codelineno-14-7"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-14-8" name="__codelineno-14-8" href="#__codelineno-14-8"></a><span class="n">n1</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n2</span><span class="p">;</span>
<a id="__codelineno-14-9" name="__codelineno-14-9" href="#__codelineno-14-9"></a><span class="n">n1</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n3</span><span class="p">;</span>
<a id="__codelineno-14-10" name="__codelineno-14-10" href="#__codelineno-14-10"></a><span class="n">n2</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n4</span><span class="p">;</span>
@@ -3760,7 +3760,7 @@
<a id="__codelineno-15-5" name="__codelineno-15-5" href="#__codelineno-15-5"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="p">(</span><span class="m">3</span><span class="p">);</span>
<a id="__codelineno-15-6" name="__codelineno-15-6" href="#__codelineno-15-6"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="p">(</span><span class="m">4</span><span class="p">);</span>
<a id="__codelineno-15-7" name="__codelineno-15-7" href="#__codelineno-15-7"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="p">(</span><span class="m">5</span><span class="p">);</span>
<a id="__codelineno-15-8" name="__codelineno-15-8" href="#__codelineno-15-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-15-8" name="__codelineno-15-8" href="#__codelineno-15-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-15-9" name="__codelineno-15-9" href="#__codelineno-15-9"></a><span class="n">n1</span><span class="p">.</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n2</span><span class="p">;</span>
<a id="__codelineno-15-10" name="__codelineno-15-10" href="#__codelineno-15-10"></a><span class="n">n1</span><span class="p">.</span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n3</span><span class="p">;</span>
<a id="__codelineno-15-11" name="__codelineno-15-11" href="#__codelineno-15-11"></a><span class="n">n2</span><span class="p">.</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n4</span><span class="p">;</span>
@@ -3775,7 +3775,7 @@
<a id="__codelineno-16-5" name="__codelineno-16-5" href="#__codelineno-16-5"></a><span class="nx">n3</span><span class="w"> </span><span class="o">:=</span><span class="w"> </span><span class="nx">NewTreeNode</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<a id="__codelineno-16-6" name="__codelineno-16-6" href="#__codelineno-16-6"></a><span class="nx">n4</span><span class="w"> </span><span class="o">:=</span><span class="w"> </span><span class="nx">NewTreeNode</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span>
<a id="__codelineno-16-7" name="__codelineno-16-7" href="#__codelineno-16-7"></a><span class="nx">n5</span><span class="w"> </span><span class="o">:=</span><span class="w"> </span><span class="nx">NewTreeNode</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<a id="__codelineno-16-8" name="__codelineno-16-8" href="#__codelineno-16-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-16-8" name="__codelineno-16-8" href="#__codelineno-16-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-16-9" name="__codelineno-16-9" href="#__codelineno-16-9"></a><span class="nx">n1</span><span class="p">.</span><span class="nx">Left</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="nx">n2</span>
<a id="__codelineno-16-10" name="__codelineno-16-10" href="#__codelineno-16-10"></a><span class="nx">n1</span><span class="p">.</span><span class="nx">Right</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="nx">n3</span>
<a id="__codelineno-16-11" name="__codelineno-16-11" href="#__codelineno-16-11"></a><span class="nx">n2</span><span class="p">.</span><span class="nx">Left</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="nx">n4</span>
@@ -3789,7 +3789,7 @@
<a id="__codelineno-17-4" name="__codelineno-17-4" href="#__codelineno-17-4"></a><span class="kd">let</span> <span class="nv">n3</span> <span class="p">=</span> <span class="n">TreeNode</span><span class="p">(</span><span class="n">x</span><span class="p">:</span> <span class="mi">3</span><span class="p">)</span>
<a id="__codelineno-17-5" name="__codelineno-17-5" href="#__codelineno-17-5"></a><span class="kd">let</span> <span class="nv">n4</span> <span class="p">=</span> <span class="n">TreeNode</span><span class="p">(</span><span class="n">x</span><span class="p">:</span> <span class="mi">4</span><span class="p">)</span>
<a id="__codelineno-17-6" name="__codelineno-17-6" href="#__codelineno-17-6"></a><span class="kd">let</span> <span class="nv">n5</span> <span class="p">=</span> <span class="n">TreeNode</span><span class="p">(</span><span class="n">x</span><span class="p">:</span> <span class="mi">5</span><span class="p">)</span>
<a id="__codelineno-17-7" name="__codelineno-17-7" href="#__codelineno-17-7"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-17-7" name="__codelineno-17-7" href="#__codelineno-17-7"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-17-8" name="__codelineno-17-8" href="#__codelineno-17-8"></a><span class="n">n1</span><span class="p">.</span><span class="kr">left</span> <span class="p">=</span> <span class="n">n2</span>
<a id="__codelineno-17-9" name="__codelineno-17-9" href="#__codelineno-17-9"></a><span class="n">n1</span><span class="p">.</span><span class="kr">right</span> <span class="p">=</span> <span class="n">n3</span>
<a id="__codelineno-17-10" name="__codelineno-17-10" href="#__codelineno-17-10"></a><span class="n">n2</span><span class="p">.</span><span class="kr">left</span> <span class="p">=</span> <span class="n">n4</span>
@@ -3804,7 +3804,7 @@
<a id="__codelineno-18-5" name="__codelineno-18-5" href="#__codelineno-18-5"></a><span class="w"> </span><span class="nx">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">new</span><span class="w"> </span><span class="nx">TreeNode</span><span class="p">(</span><span class="mf">3</span><span class="p">),</span>
<a id="__codelineno-18-6" name="__codelineno-18-6" href="#__codelineno-18-6"></a><span class="w"> </span><span class="nx">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">new</span><span class="w"> </span><span class="nx">TreeNode</span><span class="p">(</span><span class="mf">4</span><span class="p">),</span>
<a id="__codelineno-18-7" name="__codelineno-18-7" href="#__codelineno-18-7"></a><span class="w"> </span><span class="nx">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">new</span><span class="w"> </span><span class="nx">TreeNode</span><span class="p">(</span><span class="mf">5</span><span class="p">);</span>
<a id="__codelineno-18-8" name="__codelineno-18-8" href="#__codelineno-18-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-18-8" name="__codelineno-18-8" href="#__codelineno-18-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-18-9" name="__codelineno-18-9" href="#__codelineno-18-9"></a><span class="nx">n1</span><span class="p">.</span><span class="nx">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">n2</span><span class="p">;</span>
<a id="__codelineno-18-10" name="__codelineno-18-10" href="#__codelineno-18-10"></a><span class="nx">n1</span><span class="p">.</span><span class="nx">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">n3</span><span class="p">;</span>
<a id="__codelineno-18-11" name="__codelineno-18-11" href="#__codelineno-18-11"></a><span class="nx">n2</span><span class="p">.</span><span class="nx">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">n4</span><span class="p">;</span>
@@ -3819,7 +3819,7 @@
<a id="__codelineno-19-5" name="__codelineno-19-5" href="#__codelineno-19-5"></a><span class="w"> </span><span class="nx">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">new</span><span class="w"> </span><span class="nx">TreeNode</span><span class="p">(</span><span class="mf">3</span><span class="p">),</span>
<a id="__codelineno-19-6" name="__codelineno-19-6" href="#__codelineno-19-6"></a><span class="w"> </span><span class="nx">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">new</span><span class="w"> </span><span class="nx">TreeNode</span><span class="p">(</span><span class="mf">4</span><span class="p">),</span>
<a id="__codelineno-19-7" name="__codelineno-19-7" href="#__codelineno-19-7"></a><span class="w"> </span><span class="nx">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">new</span><span class="w"> </span><span class="nx">TreeNode</span><span class="p">(</span><span class="mf">5</span><span class="p">);</span>
<a id="__codelineno-19-8" name="__codelineno-19-8" href="#__codelineno-19-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-19-8" name="__codelineno-19-8" href="#__codelineno-19-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-19-9" name="__codelineno-19-9" href="#__codelineno-19-9"></a><span class="nx">n1</span><span class="p">.</span><span class="nx">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">n2</span><span class="p">;</span>
<a id="__codelineno-19-10" name="__codelineno-19-10" href="#__codelineno-19-10"></a><span class="nx">n1</span><span class="p">.</span><span class="nx">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">n3</span><span class="p">;</span>
<a id="__codelineno-19-11" name="__codelineno-19-11" href="#__codelineno-19-11"></a><span class="nx">n2</span><span class="p">.</span><span class="nx">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">n4</span><span class="p">;</span>
@@ -3834,7 +3834,7 @@
<a id="__codelineno-20-5" name="__codelineno-20-5" href="#__codelineno-20-5"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="m">3</span><span class="p">);</span>
<a id="__codelineno-20-6" name="__codelineno-20-6" href="#__codelineno-20-6"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="m">4</span><span class="p">);</span>
<a id="__codelineno-20-7" name="__codelineno-20-7" href="#__codelineno-20-7"></a><span class="n">TreeNode</span><span class="w"> </span><span class="n">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">(</span><span class="m">5</span><span class="p">);</span>
<a id="__codelineno-20-8" name="__codelineno-20-8" href="#__codelineno-20-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-20-8" name="__codelineno-20-8" href="#__codelineno-20-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-20-9" name="__codelineno-20-9" href="#__codelineno-20-9"></a><span class="n">n1</span><span class="p">.</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n2</span><span class="p">;</span>
<a id="__codelineno-20-10" name="__codelineno-20-10" href="#__codelineno-20-10"></a><span class="n">n1</span><span class="p">.</span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n3</span><span class="p">;</span>
<a id="__codelineno-20-11" name="__codelineno-20-11" href="#__codelineno-20-11"></a><span class="n">n2</span><span class="p">.</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n4</span><span class="p">;</span>
@@ -3848,7 +3848,7 @@
<a id="__codelineno-21-4" name="__codelineno-21-4" href="#__codelineno-21-4"></a><span class="kd">let</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TreeNode</span>::<span class="n">new</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span>
<a id="__codelineno-21-5" name="__codelineno-21-5" href="#__codelineno-21-5"></a><span class="kd">let</span><span class="w"> </span><span class="n">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TreeNode</span>::<span class="n">new</span><span class="p">(</span><span class="mi">4</span><span class="p">);</span>
<a id="__codelineno-21-6" name="__codelineno-21-6" href="#__codelineno-21-6"></a><span class="kd">let</span><span class="w"> </span><span class="n">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TreeNode</span>::<span class="n">new</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
<a id="__codelineno-21-7" name="__codelineno-21-7" href="#__codelineno-21-7"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-21-7" name="__codelineno-21-7" href="#__codelineno-21-7"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-21-8" name="__codelineno-21-8" href="#__codelineno-21-8"></a><span class="n">n1</span><span class="p">.</span><span class="n">borrow_mut</span><span class="p">().</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">n2</span><span class="p">.</span><span class="n">clone</span><span class="p">());</span>
<a id="__codelineno-21-9" name="__codelineno-21-9" href="#__codelineno-21-9"></a><span class="n">n1</span><span class="p">.</span><span class="n">borrow_mut</span><span class="p">().</span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">n3</span><span class="p">);</span>
<a id="__codelineno-21-10" name="__codelineno-21-10" href="#__codelineno-21-10"></a><span class="n">n2</span><span class="p">.</span><span class="n">borrow_mut</span><span class="p">().</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">n4</span><span class="p">);</span>
@@ -3863,7 +3863,7 @@
<a id="__codelineno-22-5" name="__codelineno-22-5" href="#__codelineno-22-5"></a><span class="n">TreeNode</span><span class="w"> </span><span class="o">*</span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTreeNode</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span>
<a id="__codelineno-22-6" name="__codelineno-22-6" href="#__codelineno-22-6"></a><span class="n">TreeNode</span><span class="w"> </span><span class="o">*</span><span class="n">n4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTreeNode</span><span class="p">(</span><span class="mi">4</span><span class="p">);</span>
<a id="__codelineno-22-7" name="__codelineno-22-7" href="#__codelineno-22-7"></a><span class="n">TreeNode</span><span class="w"> </span><span class="o">*</span><span class="n">n5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTreeNode</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
<a id="__codelineno-22-8" name="__codelineno-22-8" href="#__codelineno-22-8"></a><span class="c1">// 构建引用指向(即指针)</span>
<a id="__codelineno-22-8" name="__codelineno-22-8" href="#__codelineno-22-8"></a><span class="c1">// 构建节点之间的引用(指针)</span>
<a id="__codelineno-22-9" name="__codelineno-22-9" href="#__codelineno-22-9"></a><span class="n">n1</span><span class="o">-&gt;</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n2</span><span class="p">;</span>
<a id="__codelineno-22-10" name="__codelineno-22-10" href="#__codelineno-22-10"></a><span class="n">n1</span><span class="o">-&gt;</span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n3</span><span class="p">;</span>
<a id="__codelineno-22-11" name="__codelineno-22-11" href="#__codelineno-22-11"></a><span class="n">n2</span><span class="o">-&gt;</span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n4</span><span class="p">;</span>
@@ -3998,11 +3998,11 @@
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>需要注意的是,插入节点可能会改变二叉树的原有逻辑结构,而删除节点通常意味着删除该节点及其所有子树。因此,在二叉树中,插入与删除操作通常是由一套操作配合完成的,以实现有实际意义的操作。</p>
<p>需要注意的是,插入节点可能会改变二叉树的原有逻辑结构,而删除节点通常意味着删除该节点及其所有子树。因此,在二叉树中,插入与删除通常是由一套操作配合完成的,以实现有实际意义的操作。</p>
</div>
<h2 id="713">7.1.3 &nbsp; 常见二叉树类型<a class="headerlink" href="#713" title="Permanent link">&para;</a></h2>
<h3 id="1_1">1. &nbsp; 完美二叉树<a class="headerlink" href="#1_1" title="Permanent link">&para;</a></h3>
<p>「完美二叉树 perfect binary tree」所有层的节点都被完全填满。在完美二叉树中,叶节点的度为 <span class="arithmatex">\(0\)</span> ,其余所有节点的度都为 <span class="arithmatex">\(2\)</span> ;若树高度为 <span class="arithmatex">\(h\)</span> ,则节点总数为 <span class="arithmatex">\(2^{h+1} - 1\)</span> ,呈现标准的指数级关系,反映了自然界中常见的细胞分裂现象。</p>
<p>如图 7-4 所示,「完美二叉树 perfect binary tree」所有层的节点都被完全填满。在完美二叉树中,叶节点的度为 <span class="arithmatex">\(0\)</span> ,其余所有节点的度都为 <span class="arithmatex">\(2\)</span> ;若树高度为 <span class="arithmatex">\(h\)</span> ,则节点总数为 <span class="arithmatex">\(2^{h+1} - 1\)</span> ,呈现标准的指数级关系,反映了自然界中常见的细胞分裂现象。</p>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>请注意,在中文社区中,完美二叉树常被称为「满二叉树」。</p>
@@ -4026,16 +4026,16 @@
<p align="center"> 图 7-7 &nbsp; 平衡二叉树 </p>
<h2 id="714">7.1.4 &nbsp; 二叉树的退化<a class="headerlink" href="#714" title="Permanent link">&para;</a></h2>
<p>图 7-8 展示了二叉树的理想与退化状态。当二叉树的每层节点都被填满时,达到“完美二叉树”;而当所有节点都偏向一侧时,二叉树退化为“链表”。</p>
<p>图 7-8 展示了二叉树的理想结构与退化结构。当二叉树的每层节点都被填满时,达到“完美二叉树”;而当所有节点都偏向一侧时,二叉树退化为“链表”。</p>
<ul>
<li>完美二叉树是理想情况,可以充分发挥二叉树“分治”的优势。</li>
<li>链表则是另一个极端,各项操作都变为线性操作,时间复杂度退化至 <span class="arithmatex">\(O(n)\)</span></li>
</ul>
<p><a class="glightbox" href="../binary_tree.assets/binary_tree_best_worst_cases.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉树的最佳与最差结构" class="animation-figure" src="../binary_tree.assets/binary_tree_best_worst_cases.png" /></a></p>
<p align="center"> 图 7-8 &nbsp; 二叉树的最佳与最差结构 </p>
<p><a class="glightbox" href="../binary_tree.assets/binary_tree_best_worst_cases.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉树的最佳结构与最差结构" class="animation-figure" src="../binary_tree.assets/binary_tree_best_worst_cases.png" /></a></p>
<p align="center"> 图 7-8 &nbsp; 二叉树的最佳结构与最差结构 </p>
<p>如表 7-1 所示,在最佳和最差结构下,二叉树的叶节点数量、节点总数、高度等达到极大或极小值。</p>
<p align="center"> 表 7-1 &nbsp; 二叉树的最佳与最差情况 </p>
<p>如表 7-1 所示,在最佳结构和最差结构下,二叉树的叶节点数量、节点总数、高度等达到极大或极小值。</p>
<p align="center"> 表 7-1 &nbsp; 二叉树的最佳结构与最差结构 </p>
<div class="center-table">
<table>
@@ -4053,17 +4053,17 @@
<td><span class="arithmatex">\(1\)</span></td>
</tr>
<tr>
<td>高度 <span class="arithmatex">\(h\)</span> 树的叶节点数量</td>
<td>高度 <span class="arithmatex">\(h\)</span> 树的叶节点数量</td>
<td><span class="arithmatex">\(2^h\)</span></td>
<td><span class="arithmatex">\(1\)</span></td>
</tr>
<tr>
<td>高度 <span class="arithmatex">\(h\)</span> 树的节点总数</td>
<td>高度 <span class="arithmatex">\(h\)</span> 树的节点总数</td>
<td><span class="arithmatex">\(2^{h+1} - 1\)</span></td>
<td><span class="arithmatex">\(h + 1\)</span></td>
</tr>
<tr>
<td>节点总数 <span class="arithmatex">\(n\)</span> 树的高度</td>
<td>节点总数 <span class="arithmatex">\(n\)</span> 树的高度</td>
<td><span class="arithmatex">\(\log_2 (n+1) - 1\)</span></td>
<td><span class="arithmatex">\(n - 1\)</span></td>
</tr>
@@ -3466,12 +3466,12 @@
<p>二叉树常见的遍历方式包括层序遍历、前序遍历、中序遍历和后序遍历等。</p>
<h2 id="721">7.2.1 &nbsp; 层序遍历<a class="headerlink" href="#721" title="Permanent link">&para;</a></h2>
<p>如图 7-9 所示,「层序遍历 level-order traversal」从顶部到底部逐层遍历二叉树,并在每一层按照从左到右的顺序访问节点。</p>
<p>层序遍历本质上属于「广度优先遍历 breadth-first traversal」,它体现了一种“一圈一圈向外扩展”的逐层遍历方式。</p>
<p>层序遍历本质上属于「广度优先遍历 breadth-first traversal, BFS」,它体现了一种“一圈一圈向外扩展”的逐层遍历方式。</p>
<p><a class="glightbox" href="../binary_tree_traversal.assets/binary_tree_bfs.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉树的层序遍历" class="animation-figure" src="../binary_tree_traversal.assets/binary_tree_bfs.png" /></a></p>
<p align="center"> 图 7-9 &nbsp; 二叉树的层序遍历 </p>
<h3 id="1">1. &nbsp; 代码实现<a class="headerlink" href="#1" title="Permanent link">&para;</a></h3>
<p>广度优先遍历通常借助“队列”来实现。队列遵循“先进先出”的规则,而广度优先遍历则遵循“逐层推进”的规则,两者背后的思想是一致的。</p>
<p>广度优先遍历通常借助“队列”来实现。队列遵循“先进先出”的规则,而广度优先遍历则遵循“逐层推进”的规则,两者背后的思想是一致的。实现代码如下:</p>
<div class="tabbed-set tabbed-alternate" data-tabs="1:12"><input checked="checked" id="__tabbed_1_1" name="__tabbed_1" type="radio" /><input id="__tabbed_1_2" name="__tabbed_1" type="radio" /><input id="__tabbed_1_3" name="__tabbed_1" type="radio" /><input id="__tabbed_1_4" name="__tabbed_1" type="radio" /><input id="__tabbed_1_5" name="__tabbed_1" type="radio" /><input id="__tabbed_1_6" name="__tabbed_1" type="radio" /><input id="__tabbed_1_7" name="__tabbed_1" type="radio" /><input id="__tabbed_1_8" name="__tabbed_1" type="radio" /><input id="__tabbed_1_9" name="__tabbed_1" type="radio" /><input id="__tabbed_1_10" name="__tabbed_1" type="radio" /><input id="__tabbed_1_11" name="__tabbed_1" type="radio" /><input id="__tabbed_1_12" name="__tabbed_1" type="radio" /><div class="tabbed-labels"><label for="__tabbed_1_1">Python</label><label for="__tabbed_1_2">C++</label><label for="__tabbed_1_3">Java</label><label for="__tabbed_1_4">C#</label><label for="__tabbed_1_5">Go</label><label for="__tabbed_1_6">Swift</label><label for="__tabbed_1_7">JS</label><label for="__tabbed_1_8">TS</label><label for="__tabbed_1_9">Dart</label><label for="__tabbed_1_10">Rust</label><label for="__tabbed_1_11">C</label><label for="__tabbed_1_12">Zig</label></div>
<div class="tabbed-content">
<div class="tabbed-block">
@@ -3760,10 +3760,10 @@
<li><strong>空间复杂度 <span class="arithmatex">\(O(n)\)</span></strong> :在最差情况下,即满二叉树时,遍历到最底层之前,队列中最多同时存在 <span class="arithmatex">\((n + 1) / 2\)</span> 个节点,占用 <span class="arithmatex">\(O(n)\)</span> 空间。</li>
</ul>
<h2 id="722">7.2.2 &nbsp; 前序、中序、后序遍历<a class="headerlink" href="#722" title="Permanent link">&para;</a></h2>
<p>相应地,前序、中序和后序遍历都属于「深度优先遍历 depth-first traversal」,它体现了一种“先走到尽头,再回溯继续”的遍历方式。</p>
<p>图 7-10 展示了对二叉树进行深度优先遍历的工作原理。<strong>深度优先遍历就像是绕着整二叉树的外围“走”一圈</strong>,在每个节点都会遇到三个位置,分别对应前序遍历、中序遍历和后序遍历。</p>
<p><a class="glightbox" href="../binary_tree_traversal.assets/binary_tree_dfs.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉搜索树的前、中、后序遍历" class="animation-figure" src="../binary_tree_traversal.assets/binary_tree_dfs.png" /></a></p>
<p align="center"> 图 7-10 &nbsp; 二叉搜索树的前、中、后序遍历 </p>
<p>相应地,前序、中序和后序遍历都属于「深度优先遍历 depth-first traversal, DFS」,它体现了一种“先走到尽头,再回溯继续”的遍历方式。</p>
<p>图 7-10 展示了对二叉树进行深度优先遍历的工作原理。<strong>深度优先遍历就像是绕着整二叉树的外围“走”一圈</strong>,在每个节点都会遇到三个位置,分别对应前序遍历、中序遍历和后序遍历。</p>
<p><a class="glightbox" href="../binary_tree_traversal.assets/binary_tree_dfs.png" data-type="image" data-width="100%" data-height="auto" data-desc-position="bottom"><img alt="二叉搜索树的前、中、后序遍历" class="animation-figure" src="../binary_tree_traversal.assets/binary_tree_dfs.png" /></a></p>
<p align="center"> 图 7-10 &nbsp; 二叉搜索树的前、中、后序遍历 </p>
<h3 id="1_1">1. &nbsp; 代码实现<a class="headerlink" href="#1_1" title="Permanent link">&para;</a></h3>
<p>深度优先搜索通常基于递归实现:</p>
@@ -4158,9 +4158,9 @@
</div>
</div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>深度优先搜索也可以基于迭代实现,有兴趣的同学可以自行研究。</p>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>深度优先搜索也可以基于迭代实现,有兴趣的读者可以自行研究。</p>
</div>
<p>图 7-11 展示了前序遍历二叉树的递归过程,其可分为“递”和“归”两个逆向的部分。</p>
<ol>
+1 -1
View File
@@ -3326,7 +3326,7 @@
</div>
<div class="admonition abstract">
<p class="admonition-title">Abstract</p>
<p>参天大树充满生命力,根深叶茂,分枝扶疏。</p>
<p>参天大树充满生命力,根深叶茂,分枝扶疏。</p>
<p>它为我们展现了数据分治的生动形态。</p>
</div>
<h2 id="_1">本章内容<a class="headerlink" href="#_1" title="Permanent link">&para;</a></h2>
+10 -10
View File
@@ -3390,24 +3390,24 @@
<li>二叉树的初始化、节点插入和节点删除操作与链表操作方法类似。</li>
<li>常见的二叉树类型有完美二叉树、完全二叉树、完满二叉树和平衡二叉树。完美二叉树是最理想的状态,而链表是退化后的最差状态。</li>
<li>二叉树可以用数组表示,方法是将节点值和空位按层序遍历顺序排列,并根据父节点与子节点之间的索引映射关系来实现指针。</li>
<li>二叉树的层序遍历是一种广度优先搜索方法,它体现了“一圈一圈向外”的层遍历方式,通常通过队列来实现。</li>
<li>前序、中序、后序遍历皆属于深度优先搜索,它们体现了“走到尽头,再回继续”的回溯遍历方式,通常使用递归来实现。</li>
<li>二叉树的层序遍历是一种广度优先搜索方法,它体现了“一圈一圈向外扩展”的层遍历方式,通常通过队列来实现。</li>
<li>前序、中序、后序遍历皆属于深度优先搜索,它们体现了“走到尽头,再回继续”的遍历方式,通常使用递归来实现。</li>
<li>二叉搜索树是一种高效的元素查找数据结构,其查找、插入和删除操作的时间复杂度均为 <span class="arithmatex">\(O(\log n)\)</span> 。当二叉搜索树退化为链表时,各项时间复杂度会劣化至 <span class="arithmatex">\(O(n)\)</span></li>
<li>AVL 树,也称平衡二叉搜索树,它通过旋转操作确保在不断插入和删除节点后树仍然保持平衡。</li>
<li>AVL 树,也称平衡二叉搜索树,它通过旋转操作确保在不断插入和删除节点后树仍然保持平衡。</li>
<li>AVL 树的旋转操作包括右旋、左旋、先右旋再左旋、先左旋再右旋。在插入或删除节点后,AVL 树会从底向顶执行旋转操作,使树重新恢复平衡。</li>
</ul>
<h3 id="2-q-a">2. &nbsp; Q &amp; A<a class="headerlink" href="#2-q-a" title="Permanent link">&para;</a></h3>
<div class="admonition question">
<p class="admonition-title">对于只有一个节点的二叉树,树的高度和根节点的深度都是 <span class="arithmatex">\(0\)</span> 吗?</p>
<p>是的,因为高度和深度通常定义为“走过边的数量”。</p>
<p>是的,因为高度和深度通常定义为“经过的边的数量”。</p>
</div>
<div class="admonition question">
<p class="admonition-title">二叉树中的插入与删除一般都是由一套操作配合完成,这里的“一套操作”指什么呢?可以理解为资源的子节点的资源释放吗?</p>
<p>拿二叉搜索树来举例,删除节点操作要分三种情况处理,其中每种情况都需要进行多个步骤的节点操作。</p>
<p class="admonition-title">二叉树中的插入与删除一般由一套操作配合完成,这里的“一套操作”指什么呢?可以理解为资源的子节点的资源释放吗?</p>
<p>拿二叉搜索树来举例,删除节点操作要分三种情况处理,其中每种情况都需要进行多个步骤的节点操作。</p>
</div>
<div class="admonition question">
<p class="admonition-title">为什么 DFS 遍历二叉树有前、中、后三种顺序,分别有什么用呢?</p>
<p>DFS 的前、中、后序遍历和访问数组的顺序类似,是遍历二叉树的基本方法,利用这三种遍历方法,我们可以得到一个特定顺序的遍历结果。例如在二叉搜索树中,由于节点大小满足 <code>左子节点值 &lt; 根节点值 &lt; 右子节点值</code> ,因此我们只要按照 <code>-&gt;根-&gt;</code> 的优先级遍历树,就可以获得有序的节点序列。</p>
<p>与顺序和逆序遍历数组类似,前序、中序、后序遍历是三种二叉树遍历方法,我们可以使用它们得到一个特定顺序的遍历结果。例如在二叉搜索树中,由于节点大小满足 <code>左子节点值 &lt; 根节点值 &lt; 右子节点值</code> ,因此我们只要按照 <code> $\rightarrow$ 根 $\rightarrow$ </code> 的优先级遍历树,就可以获得有序的节点序列。</p>
</div>
<div class="admonition question">
<p class="admonition-title">右旋操作是处理失衡节点 <code>node</code><code>child</code><code>grand_child</code> 之间的关系,那 <code>node</code> 的父节点和 <code>node</code> 原来的连接不需要维护吗?右旋操作后岂不是断掉了?</p>
@@ -3418,8 +3418,8 @@
<p>主要看方法的使用范围,如果方法只在类内部使用,那么就设计为 <code>private</code> 。例如,用户单独调用 <code>updateHeight()</code> 是没有意义的,它只是插入、删除操作中的一步。而 <code>height()</code> 是访问节点高度,类似于 <code>vector.size()</code> ,因此设置成 <code>public</code> 以便使用。</p>
</div>
<div class="admonition question">
<p class="admonition-title">请问如何从一组输入数据构建一二叉搜索树?根节点的选择是不是很重要?</p>
<p>是的,构建树的方法已在二叉搜索树代码中的 <code>build_tree()</code> 方法中给出。至于根节点的选择,我们通常会将输入数据排序,然后中点元素作为根节点,再递归地构建左右子树。这样做可以最大程度保证树的平衡性。</p>
<p class="admonition-title">如何从一组输入数据构建一二叉搜索树?根节点的选择是不是很重要?</p>
<p>是的,构建树的方法已在二叉搜索树代码中的 <code>build_tree()</code> 方法中给出。至于根节点的选择,我们通常会将输入数据排序,然后中点元素作为根节点,再递归地构建左右子树。这样做可以最大程度保证树的平衡性。</p>
</div>
<div class="admonition question">
<p class="admonition-title">在 Java 中,字符串对比是否一定要用 <code>equals()</code> 方法?</p>
@@ -3428,7 +3428,7 @@
<li><code>==</code> :用来比较两个变量是否指向同一个对象,即它们在内存中的位置是否相同。</li>
<li><code>equals()</code>:用来对比两个对象的值是否相等。</li>
</ul>
<p>因此如果要对比值,我们通常会<code>equals()</code> 。然而,通过 <code>String a = "hi"; String b = "hi";</code> 初始化的字符串都存储在字符串常量池中,它们指向同一个对象,因此也可以用 <code>a == b</code> 来比较两个字符串的内容。</p>
<p>因此如果要对比值,我们应该使<code>equals()</code> 。然而,通过 <code>String a = "hi"; String b = "hi";</code> 初始化的字符串都存储在字符串常量池中,它们指向同一个对象,因此也可以用 <code>a == b</code> 来比较两个字符串的内容。</p>
</div>
<div class="admonition question">
<p class="admonition-title">广度优先遍历到最底层之前,队列中的节点数量是 <span class="arithmatex">\(2^h\)</span> 吗?</p>