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.

Solution:

/**
 * 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 == NULL ) return false;
        if ( root->left == NULL and root->right == NULL ) return (root->val == sum);
        bool left = false, right = false;
        left = hasPathSum(root->left, sum - root->val);
        right = hasPathSum(root->right, sum - root->val);
        return (left or right);
    }
};

Notes
For the following given binary tree and sum = 1

     1
    / 
   2

Return false!