LeetCode: 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 binary tree  
  * struct TreeNode {  
  *   int val;  
  *   TreeNode *left;  
  *   TreeNode *right;  
  *   TreeNode(int x) : val(x), left(NULL), right(NULL) {}  
  * };  
  */

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