// Time:  O(nlogn + n * t), t is the value of target.
// Space: O(t)

class Solution {
public:
    int combinationSum4(vector<int>& nums, int target) {
        vector<int> dp(target + 1, 0);
        dp[0] = 1;
        sort(nums.begin(), nums.end());

        for (int i = 1; i <= target; ++i) {
            for (int j = 0; j < nums.size() && nums[j] <= i; ++j) {
                dp[i] += dp[i - nums[j]];
            }
        }

        return dp[target];
    }
};