Maximum Unique-Character Coverage With Non-Overlapping Words

Problem: Maximum Unique-Character Coverage With Non-Overlapping Words Given a list of lowercase words words, choose a subset such that: No two chosen words share any common letter (i.e., their character sets are pairwise disjoint). Subject to that constraint, maximize the number of unique characters covered by the chosen subset. Return the maximum possible number of unique characters. Notes If a word contains duplicate letters within itself (e.g., "apple"), it can never be part of a valid subset (even alone it violates uniqueness), so it can be treated as invalid/unselectable. Alphabet is limited to a-z. Input / Output Input: Line 1: integer n (number of words) Next n lines: one word per line Output: One integer: the maximum number of unique letters that can be covered. Constraints (suggested) 1 <= n <= 20 (larger requires pruning/bitmask optimization) 1 <= len(word) <= 26 Words contain only a-z Example Input: 12 jan feb mar apr may jun jul aug sep oct nov dec Output: 9 Explanation: For example, selecting feb + may + jun covers {f,e,b,m,a,y,j,u,n} which is 9 unique letters. Note that jan and may both contain a, so they cannot be selected together. Example Input 12 jan feb mar apr may jun jul aug sep oct nov dec Output 9