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Practice Decode String

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Medium#394
LeetCode Problem

Decode String

StringStackRecursion

Problem Statement

Given an encoded string, return its decoded string. The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is guaranteed to be a positive integer. You may assume that the input string is always valid; there are no extra white spaces, square brackets are well-formed, etc. Furthermore, you may assume that the original data does not contain any digits and that digits are only for those repeat numbers, k. For example, there will not be input like 3a or 2[4]. The test cases are generated so that the length of the output will never exceed 10^5 (100,000).

Source: Decode String on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input
s = "3[a]2[bc]"
Output
"aaabcbc"

# Example 2

Input
s = "3[a2[c]]"
Output
"accaccacc"

# Example 3

Input
s = "2[abc]3[cd]ef"
Output
"abcabccdcdcdef"

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].

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← Previous UTF-8 ValidationNext → Longest Substring with At Least K Repeating Characters

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