Question
Given a string s, return the length of the longest substring that appears at least twice in s (the two occurrences may overlap). If no character repeats in a way that yields a duplicated substring, return 0. For example, "banana" has "ana" of length 3 appearing twice. The string can be up to a few thousand characters, so the intended approach binary-searches the answer length and uses hashing to test each candidate length.
longest_dup_substring_len(s: str) → int["banana"]out3State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.