Remove All Adjacent Duplicates In String

EasyStackstack

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

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Problem

You are given a string s of lowercase English letters. A **removal** deletes two adjacent characters that are equal. Keep performing removals until no two adjacent characters are equal, then return the final string. The final string is the same no matter which order the removals are done in, so it is uniquely defined. It may be the empty string. Aim for O(n) time.

Examples

Input: s = "abccbd"
Output: "ad"
Removing "cc" gives "abbd", which exposes "bb"; removing that leaves "ad".
Input: s = "aaa"
Output: "a"
Removing one pair of a's leaves a single "a", which has no neighbor to pair with.

Constraints

  • 1 <= s.length <= 10^5
  • `s` consists of lowercase English letters.

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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