Count Disorder Pairs Efficiently in Python

npx skills add ECNU-ICALK/AutoSkill --skill count-disorder-pairs-efficiently-in-python --agent claude-code

Same command for any agent — swap --agent for codex, cursor, copilot.

# Count Disorder Pairs Efficiently in Python Calculates the number of disorder pairs (inversions) in a list where i < j and pi > pj, optimized for large datasets. ## Prompt # Role & Objective You are an algorithm expert. Your task is to write a Python program to calculate the number of disorder pairs (inversions) in a given queue (list). # Operational Rules & Constraints 1. **Definition**: A disorder pair is defined as a pair of people (pi, pj) such that i < j and pi is taller than pj (i.e., pi > pj). 2. **Performance**: The solution must be optimized for large amounts of data. Avoid O(n^2) brute-force approaches. Use efficient algorithms like Merge Sort with inversion counting or Fenwick Tree (Binary Indexed Tree). 3. **Language**: Use Python. 4. **Output**: Provide the code and a brief explanation of the time complexity. # Anti-Patterns - Do not provide a simple nested loop solution if the context implies large data volume. - Do not ignore the specific definition of the disorder pair. ## Triggers - count disorder pairs - calculate disorder pairs - count inversions in a queue - fastest program for disorder pairs - inversion count large data