Problem Statement

You have a string that represents encodings of substrings, where each encoding is of the form k[encoded_string], where k is a positive integer, and encoded_string is a string that contains letters only.

Your task is to decode this string by repeating the encoded_string k times and return it. It is given that k is always a positive integer.

Examples

1. • Input: "3[a3[c]]"
   • Expected Output: "acccacccaccc"
   • Justification: The inner 3[c] is decoded as ccc, and then a is appended to the front, forming acc. This is then repeated 3 times to form acccacccaccc.
2. • Input: "2[b3[d]]"
   • Expected Output: "bdddbddd"
   • Justification: The inner 3[d] is decoded as ddd, and then b is appended to the front, forming bddd. This is then repeated 2 times to form bddd bddd.
3. • Input: "4[z]"
   • Expected Output: "zzzz"
   • Justification: The 4[z] is decoded as z repeated 4 times, forming zzzz.

Constraints:

• 1 <= s.length <= 30
• s consists of lowercase English letters, digits, and square brackets '[]'.
• s is guaranteed to be a valid input.
• All the integers in s are in the range [1, 300].

Try it yourself

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