0112._path_sum.md

112. Path Sum

难度: Easy

刷题内容

原题连接

• https://leetcode.com/problems/path-sum/

内容描述

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.

Note: A leaf is a node with no children.

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.

解题方案

思路 1 - 时间复杂度: O(N)- 空间复杂度: O(1)******

Easy

递归

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