377. Combination Sum IV - LeetCode Solution

class Solution:
    def combinationSum4(self, nums: List[int], target: int) -> int:
        dp = [-1] * (target+1)


        def trav( ans):
            if ans == 0:

                return 1
            if ans < 0:
                return 0

            if dp[ans] !=-1:
                return dp[ans]


            dp[ans] = 0
            for j in range(0, len(nums), 1):


                dp[ans] += trav(ans - nums[j])

            return dp[ans]



        return trav(target)