【LeetCode】543. 二叉樹的周長

問題描述

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.

給定一個二叉樹，你需要計算樹的直徑的長度。二叉樹的直徑是樹中任意兩個節點之間最長路徑的長度。此路徑可以通過根目錄，也可以不通過根目錄。

注：兩個節點之間的路徑長度由節點之間的邊數表示。

給定一個二叉樹

          1
         / \
        2   3
       / \     
      4   5    

返回 3, 爲路徑 [4,2,1,3] 或者 [5,2,1,3] 的長度.

Python 實現

# 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))

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