LeetCode:Path Sum

题目描述：

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.

代码：

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