leetcode 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]

 1 bool hasPathSum(TreeNode *root, int sum)
 2     {
 3         if (root == NULL)
 4             return false;
 5
 6         if (root->left == NULL && root->right == NULL) // leaf node
 7             return (root->val == sum);
 8
 9         return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);
10     }