Merge pull request #2075 from jianghongcheng/master

跟新python代码，已经检查

problems/0104.二叉树的最大深度.md

@@ -419,86 +419,107 @@ class solution:
         return 1 + max(self.maxdepth(root.left), self.maxdepth(root.right))
 ```
 
-迭代法：
+层序遍历迭代法：
 ```python
-import collections
-class solution:
-    def maxdepth(self, root: treenode) -> int:
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def maxDepth(self, root: TreeNode) -> int:
         if not root:
             return 0
-        depth = 0 #记录深度
-        queue = collections.deque()
-        queue.append(root)
+        
+        depth = 0
+        queue = collections.deque([root])
+        
         while queue:
-            size = len(queue)
             depth += 1
-            for i in range(size):
+            for _ in range(len(queue)):
                 node = queue.popleft()
                 if node.left:
                     queue.append(node.left)
                 if node.right:
                     queue.append(node.right)
+        
         return depth
+
 ```
 
 ### 559.n叉树的最大深度 
 
 递归法：
 ```python
-class solution:
-    def maxdepth(self, root: 'node') -> int:
+class Solution:
+    def maxDepth(self, root: 'Node') -> int:
         if not root:
             return 0
-        depth = 0
-        for i in range(len(root.children)):
-            depth = max(depth, self.maxdepth(root.children[i]))
-        return depth + 1
+        
+        max_depth = 1
+        
+        for child in root.children:
+            max_depth = max(max_depth, self.maxDepth(child) + 1)
+        
+        return max_depth
 ```
 
 迭代法：
 ```python
-import collections
-class solution:
-    def maxdepth(self, root: 'node') -> int:
-        queue = collections.deque()
-        if root:
-            queue.append(root)
-        depth = 0 #记录深度
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val=None, children=None):
+        self.val = val
+        self.children = children
+"""
+
+class Solution:
+    def maxDepth(self, root: TreeNode) -> int:
+        if not root:
+            return 0
+        
+        depth = 0
+        queue = collections.deque([root])
+        
         while queue:
-            size = len(queue)
             depth += 1
-            for i in range(size):
+            for _ in range(len(queue)):
                 node = queue.popleft()
-                for j in range(len(node.children)):
-                    if node.children[j]:
-                        queue.append(node.children[j])
+                for child in node.children:
+                    queue.append(child)
+        
         return depth
+
 ```
 
-使用栈来模拟后序遍历依然可以
+使用栈
 ```python
-class solution:
-    def maxdepth(self, root: 'node') -> int:
-        st = []
-        if root:
-            st.append(root)
-        depth = 0
-        result = 0
-        while st:
-            node = st.pop()
-            if node != none:
-                st.append(node) #中
-                st.append(none)
-                depth += 1
-                for i in range(len(node.children)): #处理孩子
-                    if node.children[i]:
-                        st.append(node.children[i])
-                    
-            else:
-                node = st.pop()
-                depth -= 1
-            result = max(result, depth)
-        return result
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val=None, children=None):
+        self.val = val
+        self.children = children
+"""
+
+class Solution:
+    def maxDepth(self, root: 'Node') -> int:
+        if not root:
+            return 0
+        
+        max_depth = 0
+        
+        stack = [(root, 1)]
+        
+        while stack:
+            node, depth = stack.pop()
+            max_depth = max(max_depth, depth)
+            for child in node.children:
+                stack.append((child, depth + 1))
+        
+        return max_depth
 ```