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Learn Data Structures and Algorithms in C#

Problem: Decode String

Explore how to decode encoded strings formatted with repeat counts and nested brackets by using stacks in C#. Learn to manage nested patterns and combine decoded substrings systematically, enhancing your skills in string manipulation and stack-based problem solving.

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Statement

Given an encoded string s, return its decoded string.

The encoding rule follows the format k[encoded_string], where the encoded_string enclosed within the square brackets is repeated exactly k times. The value k is guaranteed to be a positive integer.

You may assume that the input string is always valid: there are no extra whitespace characters, and all square brackets are well formed. Additionally, the original data contains no digit characters; digits appear only as repeat counts (k). For instance, inputs such as 3a or 2[4] will not occur.

The test cases are constructed such that the length of the decoded output never exceeds 10510^5.

Note: Nested encodings are possible, such as k1[string1 k2[string2]], where inner patterns are decoded first before the outer repetition is applied.

Constraints:

  • 1≤1 \leq s.Length ≤30\leq 30

  • s consists of lowercase English letters, digits, and square brackets '[' and ']'

  • s is guaranteed to be a valid input

  • All integers in s are in the range [1,300][1, 300] ...