Remove All Adjacent Duplicates in String

Problem Given a string, repeatedly remove any two adjacent equal characters. A removal can bring new neighbours together, so keep removing until no adjacent pair of equal characters remains. Return the final string.

Input / Output

• Input: a string s.
• Output: the string after all possible adjacent-duplicate removals.

Constraints

• 1 <= |s| <= 10^5. Lowercase letters (clarify).
• The result may be empty.

Example

• "abbaca" -> "ca" (remove "bb" -> "aaca", then "aa" -> "ca").
• "azxxzy" -> "ay".