Update 0104.二叉树的最大深度.md

Author: z80160280

problems/0104.二叉树的最大深度.md

@@ -281,6 +281,111 @@ class Solution {
 
 Python：
 
+104.二叉树的最大深度
+> 递归法：
+```python
+class Solution:
+    def maxDepth(self, root: TreeNode) -> int:
+        return self.getDepth(root)
+        
+    def getDepth(self, node):
+        if not node:
+            return 0
+        leftDepth = self.getDepth(node.left) #左
+        rightDepth = self.getDepth(node.right) #右
+        depth = 1 + max(leftDepth, rightDepth) #中
+        return depth
+```
+> 递归法；精简代码
+```python
+class Solution:
+    def maxDepth(self, root: TreeNode) -> int:
+        if not root:
+            return 0
+        return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))
+```
+
+> 迭代法：
+```python
+import collections
+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)
+        while queue:
+            size = len(queue)
+            depth += 1
+            for i in range(size):
+                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:
+        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
+```
+
+> 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
+        while queue:
+            size = len(queue)
+            depth += 1
+            for i in range(size):
+                node = queue.popleft()
+                for j in range(len(node.children)):
+                    if node.children[j]:
+                        queue.append(node.children[j])
+        return depth
+```
+
+> 使用栈来模拟后序遍历依然可以
+```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
+```
+
 
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