leetcode 38：path-sum

1  bool hasPathSum(TreeNode* root, int sum) {
2        if(root == NULL)
3            return false;
4         sum -= root->val;
5        if(root->left == NULL && root->right == NULL && sum == 0)
6           return true;
7        else
8            return hasPathSum(root->left, sum) || hasPathSum(root->right, sum);
9     }