Practice · 2 of 3

Sparse Inversions

CHALLENGE

Difficulty: advanced+25 XP

**Problem.** Each query: n then n values up to 1e9 (duplicates allowed). Print the number of inversions. **Constraints:** 1 ≤ n ≤ 200000; 1 ≤ a_i ≤ 10^9. Compression + Fenwick; the merge-sort W counts equal pairs.

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