CodingMediumcod-g876

Subject ParsingLevel Mid–Senior~25 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Decode a string encoded with the rule `k[encoded_string]`, where the bracketed substring is repeated `k` times. `k` is a positive integer that may have multiple digits, encodings may nest, and the input also contains plain lowercase letters outside any brackets. The input is always valid. Return the fully decoded string.

Implement

decode_string(s: str) → str

Examples

in["3[a]2[bc]"]out"aaabcbc"

What a strong answer looks like

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.

Learn the concepts

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.

Run or narrate your approach, then ask the coach.