Zolando Manipulation

Problem Overview

• Reduce a string S of A, B, C, D by repeatedly removing an A with an adjacent B or a C with an adjacent D, and return any final string with no further moves.
• Input: S with length 0..250,000 and only A/B/C/D; Output: any irreducible string reachable by these rules.
• Context: models string reduction and adjacent pair cancellation in parsing/data cleanup; a classic coding interview problem.
• Company: Zolando Manipulation interview question; implement solution for String S.