【LeetCode】543. 二叉树的周长

问题描述

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.

Note: The length of path between two nodes is represented by the number of edges between them.

给定一个二叉树，你需要计算树的直径的长度。二叉树的直径是树中任意两个节点之间最长路径的长度。此路径可以通过根目录，也可以不通过根目录。

注：两个节点之间的路径长度由节点之间的边数表示。

给定一个二叉树

          1
         / \
        2   3
       / \     
      4   5    

返回 3, 为路径 [4,2,1,3] 或者 [5,2,1,3] 的长度.

Python 实现

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def diameterOfBinaryTree(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if root == None:
            return 0
        
        diameter = self.maxDepth(root.left) + self.maxDepth(root.right)
        return max(diameter, 
                   self.diameterOfBinaryTree(root.left), 
                   self.diameterOfBinaryTree(root.right))
        
        
    def maxDepth(self, node):
        if node == None:
            return 0
        
        return 1 + max(self.maxDepth(node.left), self.maxDepth(node.right))

链接：https://leetcode.com/problems/diameter-of-binary-tree/