[leetCode刷题笔记]494. Target Sum

用递归做，但是比较慢。网上有用动态规划做的

http://blog.csdn.net/hit0803107/article/details/54894227

public class Solution {    int res = 0;    public int findTargetSumWays(int[] nums, int S) {        if (nums == null || nums.length == 0) return res;        helper(S, 0, 0, nums);        return res;    }    private void helper(int S, int sum, int pos, int[] nums) {        if (sum == S && nums.length == pos) {            res++;        }        else if (nums.length == pos) {            return;        }        else {            helper(S, sum + nums[pos], pos + 1, nums);            helper(S, sum - nums[pos], pos + 1, nums);        }    }}