Diameter of Binary Tree(递归含条件判断)
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 thelongestpath between any two nodes in a tree. This path may or may not pass through the root.
Example: Given a binary tree
1
/ \
2 3
/ \
4 5
Return3, which is the length of the path [4,2,1,3] or [5,2,1,3].
Note:The length of path between two nodes is represented by the number of edges between them.
分析
递归返回depth,但是同时在递归里更新全局变量diameter,不返回而已。这里把getDepth函数作为内置函数
注意内置函数写法,里面不含任何self,除了使用的全局变量。
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def diameterOfBinaryTree(self, root):
"""
:type root: TreeNode
:rtype: int
"""
self.d = 0
def depth(root):
if not root:
return 0
l,r = depth(root.left),depth(root.right)
self.d = max(self.d,l+r)
return 1+ max(l,r)
depth(root)
return self.d
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