LeetCode:Path Sum

题目描写叙述：

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);
}