Maximum Unique Characters Subset of Words

Given a list of words words (lowercase strings), select a subset (each word at most once) such that after concatenating the selected words: No character appears more than once in the concatenated result. Subject to that constraint, the number of distinct characters (equivalently, total length) is maximized. Output any one optimal subset as a list of words. Notes If a word contains duplicate letters within itself, it can never be selected. If multiple optimal subsets exist, return any. Input Line 1: integer n Next n lines: one word per line Output The chosen words, one per line (any order). Print an empty line for empty set. Constraints Alphabet is a..z Typical interview constraint: n <= 20 (enables backtracking/bitmask DP). Example: Input: 4 jan feb mar may One valid optimal output: jan feb Example Input 4 jan feb mar may Output jan feb