Leetcode#112 Path Sum

 1 bool solve(TreeNode *root, int sum) {
 2   if (!root->left && !root->right)
 3     return sum == root->val;
 4 
 5   return (root->left && solve(root->left, sum - root->val)) || (root->right && solve(root->right, sum - root->val));
 6 }
 7 
 8 bool hasPathSum(TreeNode *root, int sum) {
 9   if (!root)
10     return false;
11 
12   return solve(root, sum);
13 }