Leetcode 805. Split Array With Same Average

Determine if nums can be split into two non-empty subsets with the same average — equivalently, check whether there exists a subset of size k (1 ≤ k < n) whose sum equals k * total_sum / n. This reduces to a size-constrained subset-sum problem (solvable via DP or meet-in-the-middle given n ≤ 30).