Maximum Unique Character Subset

Requirements Q1 — Correct the starter code. Before changing the algorithm, find and fix any off-by-one error or incorrect count handling for empty input and words containing duplicate letters. Q2 — Handle small inputs (about 12 words). Use straightforward backtracking. For every word, branch between taking it and skipping it, carry a 26-bit integer mask of letters already selected, and reject a word when its mask overlaps the current mask. Return the selected subset itself…