Make All Elements Distinct (Amazon London)

Problem Overview

• Given an array of product identifiers, find the minimum number of leftmost removals needed so all remaining identifiers are distinct.
• Input: n and identifier[n]; Output: an integer for the minimal operations.
• Real-world context: Amazon warehouse inventory where duplicate IDs must be eliminated by trimming the start of the sequence.
• Amazon London interview question: a coding interview problem asked in Amazon interviews, suitable for a coding interview practice.