PathSum*

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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.

Note: A leaf is a node with no children.

Example:

Given the below binary tree and sum = 22,
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i write lots of rows but it is error,the answer is just  3 rows,so i do not unstand recursion 

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