LeetCode | 0543. Diameter of Binary Tree二叉树的直径【Python】
LeetCode 0543. Diameter of Binary Tree二叉树的直径【Easy】【Python】【递归】
Problem
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.
Example:
Given a binary tree
1
/ \
2 3
/ \
4 5
Return 3, 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.
问题
给定一棵二叉树,你需要计算它的直径长度。一棵二叉树的直径长度是任意两个结点路径长度中的最大值。这条路径可能穿过根结点。
示例 :
给定二叉树
1
/ \
2 3
/ \
4 5
返回 3, 它的长度是路径 [4,2,1,3] 或者 [5,2,1,3]。
注意: 两结点之间的路径长度是以它们之间边的数目表示。
思路
递归
不是求左子树高度 + 右子树高度。
而是求任意两点之间的路径最大值。
Python3代码
# 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: TreeNode) -> int:
self.max = 0
self.depth(root)
return self.max
def depth(self, root):
if not root:
return 0
l = self.depth(root.left)
r = self.depth(root.right)
# 更新最大值
self.max = max(self.max, l + r)
# 返回高度
return max(l, r) + 1
代码地址
最怕一生碌碌无为,还说平凡难能可贵。