Question
Decode a nested run-length encoded string. The encoding rule is k[encoded] where the bracketed substring is repeated k times; k is a positive integer (possibly multi-digit) and brackets may nest, e.g. '3[a2[bc]]' -> 'abcbcabcbcabcbc'. Plain letters appear as themselves. The input contains only lowercase letters, digits, and the brackets, and is guaranteed valid. Return the fully expanded string.
decode_string(s: str) → str["3[a2[bc]]"]out"abcbcabcbcabcbc"State 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.