add python leetcode 543

python-leetcode/README.md

@@ -36,6 +36,7 @@
 22. [左右叶子之和](./solution/tree/leetcode_404_.py)
 23. [路径总和 III](./solution/tree/leetcode_437_.py)
 24. [二叉树的堂兄弟节点](./solution/tree/leetcode_993_.py)
+25. [二叉树的直径](./solution/tree/leetcode_543_.py)
 
 
 

python-leetcode/solution/tree/leetcode_543_.py

+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# coding=utf-8
+"""
+543. 二叉树的直径
+"""
+from solution import TreeNode
+
+
+class Solution:
+    max = 0
+
+    def diameterOfBinaryTree(self, root: TreeNode) -> int:
+
+        if not root or (not root.left and not root.right):
+            return 0
+
+        def helper(root: TreeNode):
+            if not root:
+                return 0
+
+            a = helper(root.left) + 1
+            b = helper(root.right) + 1
+            #记录某个节点的最大直径
+            self.max = self.max if a + b - 2 < self.max else a + b - 2
+            res = a if a > b else b
+            return res
+
+        helper(root)
+
+        return self.max