Add the code to the docs.

codes/cpp/chapter_tree/binary_tree_bfs.cpp

@@ -15,12 +15,12 @@ vector<int> hierOrder(TreeNode* root) {
     vector<int> vec;
     while (!queue.empty()) {
         TreeNode* node = queue.front();
-        queue.pop();  // 队列出队
+        queue.pop();                 // 队列出队
-        vec.push_back(node->val);            // 保存结点
+        vec.push_back(node->val);    // 保存结点
         if (node->left != nullptr)
-            queue.push(node->left);    // 左子结点入队
+            queue.push(node->left);  // 左子结点入队
         if (node->right != nullptr)
-            queue.push(node->right);   // 右子结点入队
+            queue.push(node->right); // 右子结点入队
     }
     return vec;
 }

codes/python/chapter_tree/binary_tree.py

@@ -12,13 +12,14 @@ from include import *
 
 """ Driver Code """
 if __name__ == "__main__":
-    # 初始化二叉树
+    """ 初始化二叉树 """
     # 初始化节点
     n1 = TreeNode(val=1)
     n2 = TreeNode(val=2)
     n3 = TreeNode(val=3)
     n4 = TreeNode(val=4)
     n5 = TreeNode(val=5)
+    # 构建引用指向（即指针）
     n1.left = n2
     n1.right = n3
     n2.left = n4
@@ -26,15 +27,13 @@ if __name__ == "__main__":
     print("\n初始化二叉树\n")
     print_tree(n1)
 
-    # 插入与删除结点
+    """ 插入与删除结点 """
     P = TreeNode(0)
-
     # 在 n1 -> n2 中间插入节点 P
     n1.left = P
     P.left = n2
     print("\n插入结点 P 后\n")
     print_tree(n1)
-
     # 删除结点
     n1.left = n2
     print("\n删除结点 P 后\n");

codes/python/chapter_tree/binary_tree_bfs.py

@@ -14,22 +14,18 @@ from include import *
 """ 层序遍历 """
 def hier_order(root: TreeNode):
     # 初始化队列，加入根结点
-    queue: typing.Deque[TreeNode] = collections.deque()
+    queue = collections.deque()
     queue.append(root)
     # 初始化一个列表，用于保存遍历序列
-    result = []
+    res = []
     while queue:
-        # 队列出队
+        node = queue.popleft()       # 队列出队
-        node = queue.popleft()
+        res.append(node.val)         # 保存节点值
-        # 保存节点值
-        result.append(node.val)
         if node.left is not None:
-            # 左子结点入队
+            queue.append(node.left)  # 左子结点入队
-            queue.append(node.left)
         if node.right is not None:
-            # 右子结点入队
+            queue.append(node.right) # 右子结点入队
-            queue.append(node.right)
+    return res
-    return result
 
 
 """ Driver Code """
@@ -41,6 +37,6 @@ if __name__ == "__main__":
     print_tree(root)
 
     # 层序遍历
-    result = hier_order(root)
+    res = hier_order(root)
-    print("\n层序遍历的结点打印序列 = ", result)
+    print("\n层序遍历的结点打印序列 = ", res)
-    assert result == [1, 2, 3, 4, 5, 6, 7]
+    assert res == [1, 2, 3, 4, 5, 6, 7]

codes/python/chapter_tree/binary_tree_dfs.py

@@ -11,40 +11,34 @@ sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
 
-result = []
+res = []
 
-
+""" 前序遍历 """
-""" 前序遍历二叉树 """
 def pre_order(root: typing.Optional[TreeNode]):
     if root is None:
         return
-
     # 访问优先级：根结点 -> 左子树 -> 右子树
-    result.append(root.val)
+    res.append(root.val)
     pre_order(root=root.left)
     pre_order(root=root.right)
 
-
+""" 中序遍历 """
-""" 中序遍历二叉树 """
 def in_order(root: typing.Optional[TreeNode]):
     if root is None:
         return
-
     # 访问优先级：左子树 -> 根结点 -> 右子树
     in_order(root=root.left)
-    result.append(root.val)
+    res.append(root.val)
     in_order(root=root.right)
 
-
+""" 后序遍历 """
-""" 后序遍历二叉树 """
 def post_order(root: typing.Optional[TreeNode]):
     if root is None:
         return
-
     # 访问优先级：左子树 -> 右子树 -> 根结点
     post_order(root=root.left)
     post_order(root=root.right)
-    result.append(root.val)
+    res.append(root.val)
 
 
 """ Driver Code """
@@ -56,19 +50,19 @@ if __name__ == "__main__":
     print_tree(root)
 
     # 前序遍历
-    result.clear()
+    res.clear()
     pre_order(root)
-    print("\n前序遍历的结点打印序列 = ", result)
+    print("\n前序遍历的结点打印序列 = ", res)
-    assert result == [1, 2, 4, 5, 3, 6, 7]
+    assert res == [1, 2, 4, 5, 3, 6, 7]
 
     # 中序遍历
-    result.clear()
+    res.clear()
     in_order(root)
-    print("\n中序遍历的结点打印序列 = ", result)
+    print("\n中序遍历的结点打印序列 = ", res)
-    assert result == [4, 2, 5, 1, 6, 3, 7]
+    assert res == [4, 2, 5, 1, 6, 3, 7]
 
     # 后序遍历
-    result.clear()
+    res.clear()
     post_order(root)
-    print("\n后序遍历的结点打印序列 = ", result)
+    print("\n后序遍历的结点打印序列 = ", res)
-    assert result == [4, 5, 2, 6, 7, 3, 1]
+    assert res == [4, 5, 2, 6, 7, 3, 1]

docs/chapter_tree/binary_tree.md

@@ -182,7 +182,7 @@ comments: true
 === "Python"
 
     ```python title="binary_tree.py"
-    # 初始化二叉树
+    """ 初始化二叉树 """
     # 初始化节点
     n1 = TreeNode(val=1)
     n2 = TreeNode(val=2)
@@ -302,7 +302,7 @@ comments: true
 === "Python"
 
     ```python title="binary_tree.py"
-    # 插入与删除结点
+    """ 插入与删除结点 """
     p = TreeNode(0)
     # 在 n1 -> n2 中间插入结点 P
     n1.left = p
@@ -461,7 +461,7 @@ comments: true
 === "Python"
 
     ```python title=""
-    “”“ 二叉树的数组表示 ”“”
+    """ 二叉树的数组表示 """
     # 直接使用 None 来表示空位
     tree = [1, 2, 3, 4, None, 6, 7, 8, 9, None, None, 12, None, None, 15]
     ```

docs/chapter_tree/binary_tree_traversal.md

@@ -51,12 +51,12 @@ comments: true
         vector<int> vec;
         while (!queue.empty()) {
             TreeNode* node = queue.front();
-            queue.pop();  // 队列出队
+            queue.pop();                 // 队列出队
-            vec.push_back(node->val);            // 保存结点
+            vec.push_back(node->val);    // 保存结点
             if (node->left != nullptr)
-                queue.push(node->left);    // 左子结点入队
+                queue.push(node->left);  // 左子结点入队
             if (node->right != nullptr)
-                queue.push(node->right);   // 右子结点入队
+                queue.push(node->right); // 右子结点入队
         }
         return vec;
     }
@@ -65,7 +65,21 @@ comments: true
 === "Python"
 
     ```python title="binary_tree_bfs.py"
-    
+    """ 层序遍历 """
+    def hier_order(root: TreeNode):
+        # 初始化队列，加入根结点
+        queue = collections.deque()
+        queue.append(root)
+        # 初始化一个列表，用于保存遍历序列
+        res = []
+        while queue:
+            node = queue.popleft()       # 队列出队
+            res.append(node.val)         # 保存节点值
+            if node.left is not None:
+                queue.append(node.left)  # 左子结点入队
+            if node.right is not None:
+                queue.append(node.right) # 右子结点入队
+        return res
     ```
 
 === "Go"
@@ -256,7 +270,32 @@ comments: true
 === "Python"
 
     ```python title="binary_tree_dfs.py"
+    """ 前序遍历 """
+    def pre_order(root: typing.Optional[TreeNode]):
+        if root is None:
+            return
+        # 访问优先级：根结点 -> 左子树 -> 右子树
+        res.append(root.val)
+        pre_order(root=root.left)
+        pre_order(root=root.right)
 
+    """ 中序遍历 """
+    def in_order(root: typing.Optional[TreeNode]):
+        if root is None:
+            return
+        # 访问优先级：左子树 -> 根结点 -> 右子树
+        in_order(root=root.left)
+        res.append(root.val)
+        in_order(root=root.right)
+
+    """ 后序遍历 """
+    def post_order(root: typing.Optional[TreeNode]):
+        if root is None:
+            return
+        # 访问优先级：左子树 -> 右子树 -> 根结点
+        post_order(root=root.left)
+        post_order(root=root.right)
+        res.append(root.val)
     ```
 
 === "Go"
@@ -402,7 +441,6 @@ comments: true
         postOrder(root.right);
         list.Add(root.val);
     }
-    
     ```
 
 !!! note