543

Author: tech-cow

README.md

@@ -71,7 +71,7 @@ Success is like pregnancy, Everybody congratulates you but nobody knows how many
 |110|[Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/#/description)| [Python [Yu]](./tree/Yu/110_isBalanced.py) | _O(N)_| _O(h)_  | Easy | ||
 |112|[Path Sum](https://leetcode.com/problems/path-sum/#/description)| [Python [Yu]](./tree/Yu/112_hasPathSum.py) | _O(N)_| _O(h)_  | Easy | |[中文讲解](https://www.youtube.com/watch?v=LgtcGjIuE18&feature=youtu.be)|
 |404|[Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/#/description)| [Python [Yu]](./tree/Yu/404_sum_of_Left_Leaves.py) | _O(N)_| _O(h)_  | Easy | ||
-
+|543|[Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/#/description)| [Python [Yu]](./tree/Yu/543.py) | _O(N)_| _O(h)_  | Easy | |[公瑾讲解](https://www.youtube.com/watch?v=0VnOfu2pYTo)|
 
 
 

tree/Yu/543.py

@@ -0,0 +1,40 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# Author: Yu Zhou
+
+# ****************
+# Descrption:
+# 543. Diameter of Binary Tree
+# Given a binary tree, you need to compute the length of the diameter of the tree.
+# The diameter of a binary tree is the length of the longest path between any two
+# nodes in a tree. This path may or may not pass through the root.
+# ****************
+
+# 思路：
+# 这题最重要是写一个global sum用来比对当前最大的长度，和之前保存的最大的长度
+# 因为可能subtree某个长度会高于从外围root的长度
+
+# 本人的中文视频讲解：
+# https://www.youtube.com/watch?v=0VnOfu2pYTo
+
+# ****************
+# Final Solution *
+# ****************
+class Solution(object):
+    def diameterOfBinaryTree(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        self.res = 0
+        def depth(root):
+            if not root:
+                return 0
+            left = depth(root.left)
+            right = depth(root.right)
+            self.res = max(self.res, left+right)
+            return 1+ max(left,right)
+
+        depth(root)
+        return self.res