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 execute(TreeNode* root,int sum){        sum-=root->val;        if(root->left==NULL&&root->right==NULL){            if(sum==0)                return true;        }        if(root->left&&execute(root->left,sum)){            return true;        }        if(root->right&&execute(root->right,sum)){            return true;        }        return false;    }        bool hasPathSum(TreeNode* root, int sum) {        if(root==NULL)            return false;        return execute(root,sum);     }};