3428. Maximum and Minimum Sums of at Most Size K Subsequences

You are given an integer array nums and a positive integer k. Return the sum of the maximum and minimum elements of all subsequences of nums with at most k elements. Since the answer may be very large, return it modulo 109 + 7. Example 1: Input: nums = [1,2,3], k = 2 Output: 24 Explanation: The subsequences of nums with at most 2 elements are: Subsequence Minimum Maximum Sum [1] 1 1