Bug fixes and improvements (#1298)

* Fix is_empty() implementation in the stack and queue chapter

* Update en/CONTRIBUTING.md

* Remove "剩余" from the state definition of knapsack problem

* Sync zh and zh-hant versions

* Update the stylesheets of code tabs

* Fix quick_sort.rb

* Fix TS code

* Update chapter_paperbook

* Upload the manuscript of 0.1 section

* Fix binary_tree_dfs.rb

* Bug fixes

* Update README

* Update README

* Update README

* Update README.md

* Update README

* Sync zh and zh-hant versions

* Bug fixes

zh-hant/docs/chapter_tree/array_representation_of_tree.md

@@ -123,7 +123,9 @@
 === "Ruby"
 
     ```ruby title=""
-
+    ### 二元樹的陣列表示 ###
+    # 使用 nil 來表示空位
+    tree = [1, 2, 3, 4, nil, 6, 7, 8, 9, nil, nil, 12, nil, nil, 15]
     ```
 
 === "Zig"

zh-hant/docs/chapter_tree/avl_tree.md

@@ -129,9 +129,9 @@ AVL 樹既是二元搜尋樹，也是平衡二元樹，同時滿足這兩類二
         right: TreeNode | null; // 右子節點指標
         constructor(val?: number, height?: number, left?: TreeNode | null, right?: TreeNode | null) {
             this.val = val === undefined ? 0 : val;
-            this.height = height === undefined ? 0 : height; 
-            this.left = left === undefined ? null : left; 
-            this.right = right === undefined ? null : right; 
+            this.height = height === undefined ? 0 : height;
+            this.left = left === undefined ? null : left;
+            this.right = right === undefined ? null : right;
         }
     }
     ```
@@ -214,7 +214,18 @@ AVL 樹既是二元搜尋樹，也是平衡二元樹，同時滿足這兩類二
 === "Ruby"
 
     ```ruby title=""
+    ### AVL 樹節點類別 ###
+    class TreeNode
+      attr_accessor :val    # 節點值
+      attr_accessor :height # 節點高度
+      attr_accessor :left   # 左子節點引用
+      attr_accessor :right  # 右子節點引用
 
+      def initialize(val)
+        @val = val
+        @height = 0
+      end
+    end
     ```
 
 === "Zig"

zh-hant/docs/chapter_tree/binary_tree.md

@@ -106,7 +106,7 @@
         val: number;
         left: TreeNode | null;
         right: TreeNode | null;
-    
+
         constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
             this.val = val === undefined ? 0 : val; // 節點值
             this.left = left === undefined ? null : left; // 左子節點引用
@@ -189,7 +189,16 @@
 === "Ruby"
 
     ```ruby title=""
+    ### 二元樹節點類別 ###
+    class TreeNode
+      attr_accessor :val    # 節點值
+      attr_accessor :left   # 左子節點引用
+      attr_accessor :right  # 右子節點引用
 
+      def initialize(val)
+        @val = val
+      end
+    end
     ```
 
 === "Zig"
@@ -432,7 +441,18 @@
 === "Ruby"
 
     ```ruby title="binary_tree.rb"
-
+    # 初始化二元樹
+    # 初始化節點
+    n1 = TreeNode.new(1)
+    n2 = TreeNode.new(2)
+    n3 = TreeNode.new(3)
+    n4 = TreeNode.new(4)
+    n5 = TreeNode.new(5)
+    # 構建節點之間的引用（指標）
+    n1.left = n2
+    n1.right = n3
+    n2.left = n4
+    n2.right = n5
     ```
 
 === "Zig"
@@ -594,7 +614,13 @@
 === "Ruby"
 
     ```ruby title="binary_tree.rb"
-
+    # 插入與刪除節點
+    _p = TreeNode.new(0)
+    # 在 n1 -> n2 中間插入節點 _p
+    n1.left = _p
+    _p.left = n2
+    # 刪除節點
+    n1.left = n2
     ```
 
 === "Zig"