build

docs/chapter_tree/array_representation_of_tree.md

@@ -123,6 +123,14 @@ comments: true
 === "Kotlin"
 
     ```kotlin title=""
+    /* 二叉树的数组表示 */
+    // 使用 null 来表示空位
+    val tree = mutableListOf( 1, 2, 3, 4, null, 6, 7, 8, 9, null, null, 12, null, null, 15 )
+    ```
+
+=== "Ruby"
+
+    ```ruby title=""
 
     ```
 
@@ -1240,6 +1248,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="array_binary_tree.rb"
+    [class]{ArrayBinaryTree}-[func]{}
+    ```
+
 === "Zig"
 
     ```zig title="array_binary_tree.zig"

docs/chapter_tree/avl_tree.md

@@ -211,6 +211,17 @@ AVL 树既是二叉搜索树，也是平衡二叉树，同时满足这两类二
 === "Kotlin"
 
     ```kotlin title=""
+    /* AVL 树节点类 */
+    class TreeNode(val _val: Int) {  // 节点值
+        val height: Int = 0          // 节点高度
+        val left: TreeNode? = null   // 左子节点
+        val right: TreeNode? = null  // 右子节点
+    }
+    ```
+
+=== "Ruby"
+
+    ```ruby title=""
 
     ```
 
@@ -441,6 +452,14 @@ AVL 树既是二叉搜索树，也是平衡二叉树，同时满足这两类二
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{height}
+
+    [class]{AVLTree}-[func]{update_height}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"
@@ -616,6 +635,12 @@ AVL 树既是二叉搜索树，也是平衡二叉树，同时满足这两类二
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{balance_factor}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"
@@ -885,6 +910,12 @@ AVL 树的特点在于“旋转”操作，它能够在不影响二叉树的中
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{right_rotate}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"
@@ -1140,6 +1171,12 @@ AVL 树的特点在于“旋转”操作，它能够在不影响二叉树的中
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{left_rotate}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"
@@ -1608,6 +1645,12 @@ AVL 树的特点在于“旋转”操作，它能够在不影响二叉树的中
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{rotate}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"
@@ -1991,6 +2034,14 @@ 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
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{insert}
+
+    [class]{AVLTree}-[func]{insert_helper}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"
@@ -2576,6 +2627,14 @@ 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
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="avl_tree.rb"
+    [class]{AVLTree}-[func]{remove}
+
+    [class]{AVLTree}-[func]{remove_helper}
+    ```
+
 === "Zig"
 
     ```zig title="avl_tree.zig"

docs/chapter_tree/binary_search_tree.md

@@ -310,6 +310,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_search_tree.rb"
+    [class]{BinarySearchTree}-[func]{search}
+    ```
+
 === "Zig"
 
     ```zig title="binary_search_tree.zig"
@@ -756,6 +762,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_search_tree.rb"
+    [class]{BinarySearchTree}-[func]{insert}
+    ```
+
 === "Zig"
 
     ```zig title="binary_search_tree.zig"
@@ -1512,6 +1524,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_search_tree.rb"
+    [class]{BinarySearchTree}-[func]{remove}
+    ```
+
 === "Zig"
 
     ```zig title="binary_search_tree.zig"

docs/chapter_tree/binary_tree.md

@@ -183,6 +183,16 @@ comments: true
 === "Kotlin"
 
     ```kotlin title=""
+    /* 二叉树节点类 */
+    class TreeNode(val _val: Int) {  // 节点值
+        val left: TreeNode? = null   // 左子节点引用
+        val right: TreeNode? = null  // 右子节点引用
+    }
+    ```
+
+=== "Ruby"
+
+    ```ruby title=""
 
     ```
 
@@ -414,6 +424,22 @@ comments: true
 === "Kotlin"
 
     ```kotlin title="binary_tree.kt"
+    // 初始化节点
+    val n1 = TreeNode(1)
+    val n2 = TreeNode(2)
+    val n3 = TreeNode(3)
+    val n4 = TreeNode(4)
+    val n5 = TreeNode(5)
+    // 构建节点之间的引用（指针）
+    n1.left = n2
+    n1.right = n3
+    n2.left = n4
+    n2.right = n5
+    ```
+
+=== "Ruby"
+
+    ```ruby title="binary_tree.rb"
 
     ```
 
@@ -568,6 +594,17 @@ comments: true
 === "Kotlin"
 
     ```kotlin title="binary_tree.kt"
+    val P = TreeNode(0)
+    // 在 n1 -> n2 中间插入节点 P
+    n1.left = P
+    P.left = n2
+    // 删除节点 P
+    n1.left = n2
+    ```
+
+=== "Ruby"
+
+    ```ruby title="binary_tree.rb"
 
     ```
 

docs/chapter_tree/binary_tree_traversal.md

@@ -314,6 +314,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_tree_bfs.rb"
+    [class]{}-[func]{level_order}
+    ```
+
 === "Zig"
 
     ```zig title="binary_tree_bfs.zig"
@@ -781,6 +787,16 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="binary_tree_dfs.rb"
+    [class]{}-[func]{pre_order}
+
+    [class]{}-[func]{in_order}
+
+    [class]{}-[func]{post_order}
+    ```
+
 === "Zig"
 
     ```zig title="binary_tree_dfs.zig"