leetcode377

public class Solution {

    private int[] dp;

        public int CombinationSum4(int[] nums, int target)

        {

            dp = new int[target + ];

            for (int i = ; i < dp.Length; i++)

            {

                dp[i] = -;

            }

            dp[] = ;

            return helper(nums, target);

        }

        private int helper(int[] nums, int target)

        {

            if (dp[target] != -)

            {

                return dp[target];

            }

            int res = ;

            for (int i = ; i < nums.Length; i++)

            {

                if (target >= nums[i])

                {

                    res += helper(nums, target - nums[i]);

                }

            }

            dp[target] = res;

            return res;

        }

}