Code RoomEncoded string decoder
MediumPrep Room Coding #1439

Encoded string decoder

CodingAlgorithms & data structuresMid–Senior~25 min

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.

0:00 of about 25 min
InputExpectedGot
["3[a]2[bc]"]"aaabcbc"not run yetsample