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.
bool hasPathSum(TreeNode *root, int sum) {
if(!root) return false;
if(sum == root->val && root->left == NULL && root->right == NULL) return true;
return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);
}