112. Path Sum

Posted 2020-07-28 panini

题目：

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.

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 Tree Depth-first Search 

链接：http://leetcode.com/problems/path-sum/ 

一刷，DFS

class Solution(object):
    def hasPathSum(self, root, sum):
        if not root:
            return False
        if not root.left and not root.right and sum == root.val:
            return True
        return self.hasPathSum(root.left, sum - root.val) or self.hasPathSum(root.right, sum - root.val)