[LeetCode] Path Sum

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.

/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class Solution {

public:

    int target = 0;

    bool search(TreeNode *cur, int curSum)

    {

        if(cur == NULL) return false;

        curSum += cur -> val;

        if(curSum == target && cur -> left == NULL && cur -> right == NULL) return true;

        return search(cur -> left, curSum) || search(cur -> right, curSum);

    }

    bool hasPathSum(TreeNode *root, int sum) {

        // IMPORTANT: Please reset any member data you declared, as

        // the same Solution instance will be reused for each test case.

        if(root == NULL) return false;

        target = sum;

        return search(root, 0);

    }

};