[leetcode] 112. Path Sum 解题报告

题目链接：https://leetcode.com/problems/path-sum/

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：前序遍历二叉树，到一个节点为叶子节点时判断路径和是否等于给定的值。

代码如下：

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool hasPathSum(TreeNode* root, int sum) {        if(!root) return false;        sum -= root->val;        if(!root->left && !root->right && sum==0) return true;        if(hasPathSum(root->left, sum) || hasPathSum(root->right, sum))            return true;        return false;    }};