Leetcode 3572. Maximize Y‑Sum by Picking a Triplet of Distinct X‑Values

Given paired arrays x and y, pick three indices with pairwise distinct x-values to maximize the sum of their y-values. This reduces to grouping y-values by x, taking the maximum y for each distinct x, and summing the top three such maxima (or returning -1 if fewer than three distinct x-values exist).