The Weekly Challenge

You are given a sequence of 5 lowercase letters, with one letter replaced by '?'. Each letter maps to its position in the alphabet ('a = 1', 'b = 2', ..., 'z = 26'). The sequence follows a repeating pattern of step sizes between consecutive letters. The pattern is either a constant step (e.g., '+2, +2, +2, +2') or a simple alternating pattern of two distinct steps (e.g., '+2, +3, +2, +3').

You are given an array of numbers. Write a script to find all subsets where the sum of elements equals the sum of their indices.