Leetcode-112. Path Sum

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.

思路

题目只要求返回true或者false，因此不需要记录路径。 由于只需要求出一个结果，因此，当左、右任意一棵子树求到了满意结果，都可以及时return。

代码

class Solution { public: bool hasPathSum(TreeNode* root, int sum) { if(!root) return false; if(!root->left && !root->right) return sum == root->val; return hasPathSum(root->left, sum-root->val) || hasPathSum(root->right, sum-root->val); } };