Find shortest unique substring per word

## Shortest unique substring for each word You are given an array of **distinct** strings `words`. For each word `w` in `words`, find a **non-empty contiguous substring** of `w` that **does not appear as a substring in any other word** in the array. Return, for every word, the **shortest** such substring. ### Tie-breaking If a word has multiple valid substrings with the same minimal length: 1. Choose the one with the **smallest starting index** in the word. 2. If there is still a tie, choose the **lexicographically smallest** substring. You may assume that for every word, at least one such substring exists. ### Example **Input**: ```text ['cheapair', 'cheapoair', 'peloton', 'pelican'] ``` **Output**: ```text { 'cheapair': 'pa', 'cheapoair': 'po', 'peloton': 't', 'pelican': 'li' } ``` ### Constraints (typical interview ranges) - `1 <= len(words) <= 2e3` - `1 <= len(words[i]) <= 2e3` - Total characters across all words `<= 2e4` - Lowercase English letters (you may generalize if desired)