首页 > itarticle > leetcode解题-path sum

leetcode解题-path sum

admin 11月 11, 2020 0

描述

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,
5
/
4 8
/ /
11 13 4
/
7 2 1
return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

分析

深度优先遍历可解，时间O(n)，空间O(logn)。

代码

Python

class (object):
    def hasPathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: bool
        """
        if not root:
            return False
        if not root.left and not root.right:
            return root.val == sum

        return self.hasPathSum(root.left, sum - root.val) or 
            self.hasPathSum(root.right, sum - root.val)