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krahets
2023-07-26 15:34:59 +08:00
parent 894c5a7fbf
commit c2d2bde19c
55 changed files with 285 additions and 175 deletions
@@ -3407,7 +3407,7 @@ dp[i] = \min(dp[i-1], dp[i-2]) + cost[i]
<p>本题显然具有最优子结构:我们从两个子问题最优解 <span class="arithmatex">\(dp[i-1]\)</span> , <span class="arithmatex">\(dp[i-2]\)</span> 中挑选出较优的那一个,并用它构建出原问题 <span class="arithmatex">\(dp[i]\)</span> 的最优解。</p>
<p>那么,上节的爬楼梯题目有没有最优子结构呢?它的目标是求解方案数量,看似是一个计数问题,但如果换一种问法:“求解最大方案数量”。我们意外地发现,<strong>虽然题目修改前后是等价的,但最优子结构浮现出来了</strong>:第 <span class="arithmatex">\(n\)</span> 阶最大方案数量等于第 <span class="arithmatex">\(n-1\)</span> 阶和第 <span class="arithmatex">\(n-2\)</span> 阶最大方案数量之和。所以说,最优子结构的解释方式比较灵活,在不同问题中会有不同的含义。</p>
<p>根据状态转移方程,以及初始状态 <span class="arithmatex">\(dp[1] = cost[1]\)</span> , <span class="arithmatex">\(dp[2] = cost[2]\)</span> ,可以得出动态规划代码。</p>
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<div class="highlight"><span class="filename">min_cost_climbing_stairs_dp.java</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="cm">/* 爬楼梯最小代价:动态规划 */</span>
@@ -3582,7 +3582,7 @@ dp[i] = \min(dp[i-1], dp[i-2]) + cost[i]
<p align="center"> Fig. 爬楼梯最小代价的动态规划过程 </p>
<p>本题也可以进行状态压缩,将一维压缩至零维,使得空间复杂度从 <span class="arithmatex">\(O(n)\)</span> 降低至 <span class="arithmatex">\(O(1)\)</span></p>
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<div class="highlight"><span class="filename">min_cost_climbing_stairs_dp.java</span><pre><span></span><code><a id="__codelineno-12-1" name="__codelineno-12-1" href="#__codelineno-12-1"></a><span class="cm">/* 爬楼梯最小代价:状态压缩后的动态规划 */</span>
@@ -3760,7 +3760,7 @@ dp[i, 2] = dp[i-2, 1] + dp[i-2, 2]
<p align="center"> Fig. 考虑约束下的递推关系 </p>
<p>最终,返回 <span class="arithmatex">\(dp[n, 1] + dp[n, 2]\)</span> 即可,两者之和代表爬到第 <span class="arithmatex">\(n\)</span> 阶的方案总数。</p>
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<div class="highlight"><span class="filename">climbing_stairs_constraint_dp.java</span><pre><span></span><code><a id="__codelineno-24-1" name="__codelineno-24-1" href="#__codelineno-24-1"></a><span class="cm">/* 带约束爬楼梯:动态规划 */</span>
@@ -3527,7 +3527,7 @@ dp[i, j] = \min(dp[i-1, j], dp[i, j-1]) + grid[i, j]
<li><strong>终止条件</strong>:当 <span class="arithmatex">\(i = 0\)</span><span class="arithmatex">\(j = 0\)</span> 时,返回代价 <span class="arithmatex">\(grid[0, 0]\)</span></li>
<li><strong>剪枝</strong>:当 <span class="arithmatex">\(i &lt; 0\)</span> 时或 <span class="arithmatex">\(j &lt; 0\)</span> 时索引越界,此时返回代价 <span class="arithmatex">\(+\infty\)</span> ,代表不可行。</li>
</ul>
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<div class="highlight"><span class="filename">min_path_sum.java</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="cm">/* 最小路径和:暴力搜索 */</span>
@@ -3704,7 +3704,7 @@ dp[i, j] = \min(dp[i-1, j], dp[i, j-1]) + grid[i, j]
<p>每个状态都有向下和向右两种选择,从左上角走到右下角总共需要 <span class="arithmatex">\(m + n - 2\)</span> 步,所以最差时间复杂度为 <span class="arithmatex">\(O(2^{m + n})\)</span> 。请注意,这种计算方式未考虑临近网格边界的情况,当到达网络边界时只剩下一种选择。因此实际的路径数量会少一些。</p>
<h3 id="_2">方法二:记忆化搜索<a class="headerlink" href="#_2" title="Permanent link">&para;</a></h3>
<p>我们引入一个和网格 <code>grid</code> 相同尺寸的记忆列表 <code>mem</code> ,用于记录各个子问题的解,并将重叠子问题进行剪枝。</p>
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<div class="highlight"><span class="filename">min_path_sum.java</span><pre><span></span><code><a id="__codelineno-12-1" name="__codelineno-12-1" href="#__codelineno-12-1"></a><span class="cm">/* 最小路径和:记忆化搜索 */</span>
@@ -3921,7 +3921,7 @@ dp[i, j] = \min(dp[i-1, j], dp[i, j-1]) + grid[i, j]
<h3 id="_3">方法三:动态规划<a class="headerlink" href="#_3" title="Permanent link">&para;</a></h3>
<p>基于迭代实现动态规划解法。</p>
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<div class="highlight"><span class="filename">min_path_sum.java</span><pre><span></span><code><a id="__codelineno-24-1" name="__codelineno-24-1" href="#__codelineno-24-1"></a><span class="cm">/* 最小路径和:动态规划 */</span>
@@ -4186,7 +4186,7 @@ dp[i, j] = \min(dp[i-1, j], dp[i, j-1]) + grid[i, j]
<h3 id="_4">状态压缩<a class="headerlink" href="#_4" title="Permanent link">&para;</a></h3>
<p>由于每个格子只与其左边和上边的格子有关,因此我们可以只用一个单行数组来实现 <span class="arithmatex">\(dp\)</span> 表。</p>
<p>请注意,因为数组 <code>dp</code> 只能表示一行的状态,所以我们无法提前初始化首列状态,而是在遍历每行中更新它。</p>
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<div class="highlight"><span class="filename">min_path_sum.java</span><pre><span></span><code><a id="__codelineno-36-1" name="__codelineno-36-1" href="#__codelineno-36-1"></a><span class="cm">/* 最小路径和:状态压缩后的动态规划 */</span>
@@ -3430,7 +3430,7 @@ dp[i, j] = dp[i-1, j-1]
<p>当两字符串都为空时,编辑步数为 <span class="arithmatex">\(0\)</span> ,即 <span class="arithmatex">\(dp[0, 0] = 0\)</span> 。当 <span class="arithmatex">\(s\)</span> 为空但 <span class="arithmatex">\(t\)</span> 不为空时,最少编辑步数等于 <span class="arithmatex">\(t\)</span> 的长度,即首行 <span class="arithmatex">\(dp[0, j] = j\)</span> 。当 <span class="arithmatex">\(s\)</span> 不为空但 <span class="arithmatex">\(t\)</span> 为空时,等于 <span class="arithmatex">\(s\)</span> 的长度,即首列 <span class="arithmatex">\(dp[i, 0] = i\)</span></p>
<p>观察状态转移方程,解 <span class="arithmatex">\(dp[i, j]\)</span> 依赖左方、上方、左上方的解,因此通过两层循环正序遍历整个 <span class="arithmatex">\(dp\)</span> 表即可。</p>
<h3 id="_1">代码实现<a class="headerlink" href="#_1" title="Permanent link">&para;</a></h3>
<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">Java</label><label for="__tabbed_1_2">C++</label><label for="__tabbed_1_3">Python</label><label for="__tabbed_1_4">Go</label><label for="__tabbed_1_5">JavaScript</label><label for="__tabbed_1_6">TypeScript</label><label for="__tabbed_1_7">C</label><label for="__tabbed_1_8">C#</label><label for="__tabbed_1_9">Swift</label><label for="__tabbed_1_10">Zig</label><label for="__tabbed_1_11">Dart</label><label for="__tabbed_1_12">Rust</label></div>
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<div class="highlight"><span class="filename">edit_distance.java</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="cm">/* 编辑距离:动态规划 */</span>
@@ -3727,7 +3727,7 @@ dp[i, j] = dp[i-1, j-1]
<h3 id="_2">状态压缩<a class="headerlink" href="#_2" title="Permanent link">&para;</a></h3>
<p>由于 <span class="arithmatex">\(dp[i,j]\)</span> 是由上方 <span class="arithmatex">\(dp[i-1, j]\)</span> 、左方 <span class="arithmatex">\(dp[i, j-1]\)</span> 、左上方状态 <span class="arithmatex">\(dp[i-1, j-1]\)</span> 转移而来,而正序遍历会丢失左上方 <span class="arithmatex">\(dp[i-1, j-1]\)</span> ,倒序遍历无法提前构建 <span class="arithmatex">\(dp[i, j-1]\)</span> ,因此两种遍历顺序都不可取。</p>
<p>为此,我们可以使用一个变量 <code>leftup</code> 来暂存左上方的解 <span class="arithmatex">\(dp[i-1, j-1]\)</span> ,从而只需考虑左方和上方的解。此时的情况与完全背包问题相同,可使用正序遍历。</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">Java</label><label for="__tabbed_3_2">C++</label><label for="__tabbed_3_3">Python</label><label for="__tabbed_3_4">Go</label><label for="__tabbed_3_5">JavaScript</label><label for="__tabbed_3_6">TypeScript</label><label for="__tabbed_3_7">C</label><label for="__tabbed_3_8">C#</label><label for="__tabbed_3_9">Swift</label><label for="__tabbed_3_10">Zig</label><label for="__tabbed_3_11">Dart</label><label for="__tabbed_3_12">Rust</label></div>
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<div class="highlight"><span class="filename">edit_distance.java</span><pre><span></span><code><a id="__codelineno-12-1" name="__codelineno-12-1" href="#__codelineno-12-1"></a><span class="cm">/* 编辑距离:状态压缩后的动态规划 */</span>
@@ -3421,7 +3421,7 @@
<p align="center"> Fig. 爬到第 3 阶的方案数量 </p>
<p>本题的目标是求解方案数量,<strong>我们可以考虑通过回溯来穷举所有可能性</strong>。具体来说,将爬楼梯想象为一个多轮选择的过程:从地面出发,每轮选择上 <span class="arithmatex">\(1\)</span> 阶或 <span class="arithmatex">\(2\)</span> 阶,每当到达楼梯顶部时就将方案数量加 <span class="arithmatex">\(1\)</span> ,当越过楼梯顶部时就将其剪枝。</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">Java</label><label for="__tabbed_1_2">C++</label><label for="__tabbed_1_3">Python</label><label for="__tabbed_1_4">Go</label><label for="__tabbed_1_5">JavaScript</label><label for="__tabbed_1_6">TypeScript</label><label for="__tabbed_1_7">C</label><label for="__tabbed_1_8">C#</label><label for="__tabbed_1_9">Swift</label><label for="__tabbed_1_10">Zig</label><label for="__tabbed_1_11">Dart</label><label for="__tabbed_1_12">Rust</label></div>
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<div class="highlight"><span class="filename">climbing_stairs_backtrack.java</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="cm">/* 回溯 */</span>
@@ -3694,7 +3694,7 @@ dp[i] = dp[i-1] + dp[i-2]
<li>最小子问题的解 <span class="arithmatex">\(dp[1] = 1\)</span> , <span class="arithmatex">\(dp[2] = 2\)</span> 是已知的,代表爬到第 <span class="arithmatex">\(1\)</span> , <span class="arithmatex">\(2\)</span> 阶分别有 <span class="arithmatex">\(1\)</span> , <span class="arithmatex">\(2\)</span> 种方案。</li>
</ul>
<p>观察以下代码,它和标准回溯代码都属于深度优先搜索,但更加简洁。</p>
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<div class="highlight"><span class="filename">climbing_stairs_dfs.java</span><pre><span></span><code><a id="__codelineno-12-1" name="__codelineno-12-1" href="#__codelineno-12-1"></a><span class="cm">/* 搜索 */</span>
@@ -3870,7 +3870,7 @@ dp[i] = dp[i-1] + dp[i-2]
<li>当首次计算 <span class="arithmatex">\(dp[i]\)</span> 时,我们将其记录至 <code>mem[i]</code> ,以便之后使用。</li>
<li>当再次需要计算 <span class="arithmatex">\(dp[i]\)</span> 时,我们便可直接从 <code>mem[i]</code> 中获取结果,从而将重叠子问题剪枝。</li>
</ol>
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<div class="highlight"><span class="filename">climbing_stairs_dfs_mem.java</span><pre><span></span><code><a id="__codelineno-24-1" name="__codelineno-24-1" href="#__codelineno-24-1"></a><span class="cm">/* 记忆化搜索 */</span>
@@ -4105,7 +4105,7 @@ dp[i] = dp[i-1] + dp[i-2]
<p><strong>记忆化搜索是一种“从顶至底”的方法</strong>:我们从原问题(根节点)开始,递归地将较大子问题分解为较小子问题,直至解已知的最小子问题(叶节点)。之后,通过回溯将子问题的解逐层收集,构建出原问题的解。</p>
<p>与之相反,<strong>动态规划是一种“从底至顶”的方法</strong>:从最小子问题的解开始,迭代地构建更大子问题的解,直至得到原问题的解。</p>
<p>由于动态规划不包含回溯过程,因此只需使用循环迭代实现,无需使用递归。在以下代码中,我们初始化一个数组 <code>dp</code> 来存储子问题的解,它起到了记忆化搜索中数组 <code>mem</code> 相同的记录作用。</p>
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<div class="highlight"><span class="filename">climbing_stairs_dp.java</span><pre><span></span><code><a id="__codelineno-36-1" name="__codelineno-36-1" href="#__codelineno-36-1"></a><span class="cm">/* 爬楼梯:动态规划 */</span>
@@ -4282,7 +4282,7 @@ dp[i] = dp[i-1] + dp[i-2]
<h2 id="1414">14.1.4. &nbsp; 状态压缩<a class="headerlink" href="#1414" title="Permanent link">&para;</a></h2>
<p>细心的你可能发现,<strong>由于 <span class="arithmatex">\(dp[i]\)</span> 只与 <span class="arithmatex">\(dp[i-1]\)</span><span class="arithmatex">\(dp[i-2]\)</span> 有关,因此我们无需使用一个数组 <code>dp</code> 来存储所有子问题的解</strong>,而只需两个变量滚动前进即可。</p>
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<div class="highlight"><span class="filename">climbing_stairs_dp.java</span><pre><span></span><code><a id="__codelineno-48-1" name="__codelineno-48-1" href="#__codelineno-48-1"></a><span class="cm">/* 爬楼梯:状态压缩后的动态规划 */</span>
@@ -3449,7 +3449,7 @@ dp[i, c] = \max(dp[i-1, c], dp[i-1, c - wgt[i-1]] + val[i-1])
<li><strong>终止条件</strong>:当物品编号越界 <span class="arithmatex">\(i = 0\)</span> 或背包剩余容量为 <span class="arithmatex">\(0\)</span> 时,终止递归并返回价值 <span class="arithmatex">\(0\)</span></li>
<li><strong>剪枝</strong>:若当前物品重量超出背包剩余容量,则只能不放入背包。</li>
</ul>
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<div class="highlight"><span class="filename">knapsack.java</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="cm">/* 0-1 背包:暴力搜索 */</span>
@@ -3626,7 +3626,7 @@ dp[i, c] = \max(dp[i-1, c], dp[i-1, c - wgt[i-1]] + val[i-1])
<h3 id="_2">方法二:记忆化搜索<a class="headerlink" href="#_2" title="Permanent link">&para;</a></h3>
<p>为了保证重叠子问题只被计算一次,我们借助记忆列表 <code>mem</code> 来记录子问题的解,其中 <code>mem[i][c]</code> 对应 <span class="arithmatex">\(dp[i, c]\)</span></p>
<p>引入记忆化之后,<strong>时间复杂度取决于子问题数量</strong>,也就是 <span class="arithmatex">\(O(n \times cap)\)</span></p>
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<div class="highlight"><span class="filename">knapsack.java</span><pre><span></span><code><a id="__codelineno-12-1" name="__codelineno-12-1" href="#__codelineno-12-1"></a><span class="cm">/* 0-1 背包:记忆化搜索 */</span>
@@ -3841,7 +3841,7 @@ dp[i, c] = \max(dp[i-1, c], dp[i-1, c - wgt[i-1]] + val[i-1])
<h3 id="_3">方法三:动态规划<a class="headerlink" href="#_3" title="Permanent link">&para;</a></h3>
<p>动态规划实质上就是在状态转移中填充 <span class="arithmatex">\(dp\)</span> 表的过程,代码如下所示。</p>
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<div class="highlight"><span class="filename">knapsack.java</span><pre><span></span><code><a id="__codelineno-24-1" name="__codelineno-24-1" href="#__codelineno-24-1"></a><span class="cm">/* 0-1 背包:动态规划 */</span>
@@ -4114,7 +4114,7 @@ dp[i, c] = \max(dp[i-1, c], dp[i-1, c - wgt[i-1]] + val[i-1])
</div>
</div>
<p>在代码实现中,我们仅需将数组 <code>dp</code> 的第一维 <span class="arithmatex">\(i\)</span> 直接删除,并且把内循环更改为倒序遍历即可。</p>
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<div class="highlight"><span class="filename">knapsack.java</span><pre><span></span><code><a id="__codelineno-36-1" name="__codelineno-36-1" href="#__codelineno-36-1"></a><span class="cm">/* 0-1 背包:状态压缩后的动态规划 */</span>
@@ -3541,7 +3541,7 @@ dp[i, c] = \max(dp[i-1, c], dp[i, c - wgt[i-1]] + val[i-1])
\]</div>
<h3 id="_1">代码实现<a class="headerlink" href="#_1" title="Permanent link">&para;</a></h3>
<p>对比两道题目的代码,状态转移中有一处从 <span class="arithmatex">\(i-1\)</span> 变为 <span class="arithmatex">\(i\)</span> ,其余完全一致。</p>
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<div class="highlight"><span class="filename">unbounded_knapsack.java</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="cm">/* 完全背包:动态规划 */</span>
@@ -3762,7 +3762,7 @@ dp[i, c] = \max(dp[i-1, c], dp[i, c - wgt[i-1]] + val[i-1])
</div>
</div>
<p>代码实现比较简单,仅需将数组 <code>dp</code> 的第一维删除。</p>
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<div class="highlight"><span class="filename">unbounded_knapsack.java</span><pre><span></span><code><a id="__codelineno-12-1" name="__codelineno-12-1" href="#__codelineno-12-1"></a><span class="cm">/* 完全背包:状态压缩后的动态规划 */</span>
@@ -3989,7 +3989,7 @@ dp[i, a] = \min(dp[i-1, a], dp[i, a - coins[i-1]] + 1)
<p>大多数编程语言并未提供 <span class="arithmatex">\(+ \infty\)</span> 变量,只能使用整型 <code>int</code> 的最大值来代替。而这又会导致大数越界:状态转移方程中的 <span class="arithmatex">\(+ 1\)</span> 操作可能发生溢出。</p>
<p>为此,我们采用数字 <span class="arithmatex">\(amt + 1\)</span> 来表示无效解,因为凑出 <span class="arithmatex">\(amt\)</span> 的硬币个数最多为 <span class="arithmatex">\(amt\)</span> 个。</p>
<p>最后返回前,判断 <span class="arithmatex">\(dp[n, amt]\)</span> 是否等于 <span class="arithmatex">\(amt + 1\)</span> ,若是则返回 <span class="arithmatex">\(-1\)</span> ,代表无法凑出目标金额。</p>
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<div class="highlight"><span class="filename">coin_change.java</span><pre><span></span><code><a id="__codelineno-24-1" name="__codelineno-24-1" href="#__codelineno-24-1"></a><span class="cm">/* 零钱兑换:动态规划 */</span>
@@ -4282,7 +4282,7 @@ dp[i, a] = \min(dp[i-1, a], dp[i, a - coins[i-1]] + 1)
</div>
<h3 id="_4">状态压缩<a class="headerlink" href="#_4" title="Permanent link">&para;</a></h3>
<p>零钱兑换的状态压缩的处理方式和完全背包一致。</p>
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<div class="highlight"><span class="filename">coin_change.java</span><pre><span></span><code><a id="__codelineno-36-1" name="__codelineno-36-1" href="#__codelineno-36-1"></a><span class="cm">/* 零钱兑换:状态压缩后的动态规划 */</span>
@@ -4520,7 +4520,7 @@ dp[i, a] = dp[i-1, a] + dp[i, a - coins[i-1]]
\]</div>
<p>当目标金额为 <span class="arithmatex">\(0\)</span> 时,无需选择任何硬币即可凑出目标金额,因此应将首列所有 <span class="arithmatex">\(dp[i, 0]\)</span> 都初始化为 <span class="arithmatex">\(1\)</span> 。当无硬币时,无法凑出任何 <span class="arithmatex">\(&gt;0\)</span> 的目标金额,因此首行所有 <span class="arithmatex">\(dp[0, a]\)</span> 都等于 <span class="arithmatex">\(0\)</span></p>
<h3 id="_5">代码实现<a class="headerlink" href="#_5" title="Permanent link">&para;</a></h3>
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<div class="highlight"><span class="filename">coin_change_ii.java</span><pre><span></span><code><a id="__codelineno-48-1" name="__codelineno-48-1" href="#__codelineno-48-1"></a><span class="cm">/* 零钱兑换 II:动态规划 */</span>
@@ -4748,7 +4748,7 @@ dp[i, a] = dp[i-1, a] + dp[i, a - coins[i-1]]
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<h3 id="_6">状态压缩<a class="headerlink" href="#_6" title="Permanent link">&para;</a></h3>
<p>状态压缩处理方式相同,删除硬币维度即可。</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">Java</label><label for="__tabbed_8_2">C++</label><label for="__tabbed_8_3">Python</label><label for="__tabbed_8_4">Go</label><label for="__tabbed_8_5">JavaScript</label><label for="__tabbed_8_6">TypeScript</label><label for="__tabbed_8_7">C</label><label for="__tabbed_8_8">C#</label><label for="__tabbed_8_9">Swift</label><label for="__tabbed_8_10">Zig</label><label for="__tabbed_8_11">Dart</label><label for="__tabbed_8_12">Rust</label></div>
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<div class="highlight"><span class="filename">coin_change_ii.java</span><pre><span></span><code><a id="__codelineno-60-1" name="__codelineno-60-1" href="#__codelineno-60-1"></a><span class="cm">/* 零钱兑换 II:状态压缩后的动态规划 */</span>