Minimum Operations to Make Sequence Harmonious

Problem Overview

• Given an array A of length N, compute the minimum removals to make it harmonious.
• Harmonious means the sequence can be split into groups where each group starts with k and is followed by exactly k items; the empty sequence is harmonious.
• Input: N (1≤N≤200,000) and A1..An (1≤Ai≤100,000). Output: the minimum number of deletions.
• Real-world context: validating length‑prefixed data frames or packet grouping.
• From Uber interviews; a coding interview problem and common interview question.