112. 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.

/** * 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) {        bool is_exist=false;if(root==NULL) return false;if(root->left==NULL&&root->right==NULL&&sum==root->val) return true;is_exist=hasPathSum(root->left,sum-root->val);if(is_exist) return is_exist;is_exist=hasPathSum(root->right,sum-root->val);return is_exist;    }};