这题是我蠢了，它说是组合数我就信了，言尽于此

class Solution {
public:int combinationSum4(vector<int>& nums, int target) {vector<int> dp(2000,0);dp[0]=1;for(int i=0;i<=target;i++){for(int j=0;j<nums.size();j++){if(i>=nums[j]&& dp[i] < INT_MAX - dp[i - nums[j]])dp[i]+=dp[i-nums[j]];}}return dp[target];}
};