Decode String: coding question

Problem

You get an encoded string s. The encoding rule is k[text]. This part decodes to text repeated exactly k times, and k is a positive integer.

An encoded part can be inside another encoded part. Return the decoded string.

s is always valid. It has no extra spaces, and each [ has a matching ]. Digits appear only in the repeat counts k, so the original text has no digits.

Example 1

Input:: s = "2[xy]z"
Output:: "xyxyz"

Example 2

Input:: s = "2[m3[n]]"
Output:: "mnnnmnnn"
Explanation:: The inner part 3[n] decodes to nnn. Then 2[mnnn] decodes to mnnnmnnn.

Example 3

Input:: s = "q10[r]"
Output:: "qrrrrrrrrrr"
Explanation:: A repeat count can have more than one digit.

Constraints

1 <= s.length <= 30
s has lowercase English letters, digits and the square brackets [ and ].
s is always a valid encoded string.
All integers in s are in the range [1, 300].
The decoded string has at most 10^5 characters.

SysRound wrote this statement. A reference solution checks every example.

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Bloomberg
Leetcode 394. Decode String
Reported Aug 1, 2026 · 2 source reports
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Coupang
Leetcode 394. Decode String
Reported Jun 10, 2026 · 1 source report
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Google
Leetcode 394. Decode String
Reported Dec 25, 2024 · 1 source report
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Microsoft
Leetcode 394. Decode String
Reported Oct 20, 2025 · 1 source report
SENIOR
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Problem

You get an encoded string s. The encoding rule is k[text]. This part decodes to text repeated exactly k times, and k is a positive integer.

An encoded part can be inside another encoded part. Return the decoded string.

s is always valid. It has no extra spaces, and each [ has a matching ]. Digits appear only in the repeat counts k, so the original text has no digits.

Example 1

Input:: s = "2[xy]z"
Output:: "xyxyz"

Example 2

Input:: s = "2[m3[n]]"
Output:: "mnnnmnnn"
Explanation:: The inner part 3[n] decodes to nnn. Then 2[mnnn] decodes to mnnnmnnn.

Example 3

Input:: s = "q10[r]"
Output:: "qrrrrrrrrrr"
Explanation:: A repeat count can have more than one digit.

Constraints

1 <= s.length <= 30
s has lowercase English letters, digits and the square brackets [ and ].
s is always a valid encoded string.
All integers in s are in the range [1, 300].
The decoded string has at most 10^5 characters.

SysRound wrote this statement. A reference solution checks every example.

Decode String

Problem

Example 1

Example 2

Example 3

Constraints

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Decode String

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