```
class Solution {
public:
bool hasPathSum(TreeNode* root, int sum) {
if (root == NULL) {
return false;
}
// reach leaf node
if (root->val == sum && root->left == NULL && root->right == NULL) {
return true;
}
return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);
}
};
```