CustomCC0-1.0#ct-p6-042450
Persistent K-th with Point Updates
Summary
- •Phase 6 / combined-techniques
- •Reasoning-first competitive programming drill
Problem Description
Array supports point updates creating new versions. Query k-th smallest on range [l,r] for any version.
How to read this problem in plain language:
- This is a Phase 6 reasoning drill focused on combined-techniques.
- Typical lenses to test first: persistent-segment-tree, order-statistics, offline.
- Constraints reminder: n,q <= 2e5
Mini examples for mental simulation:
1) Boundary example: Should return range minimum. Explain expected behavior and why naive logic may fail.
2) Adversarial example: Should return range maximum. Explain expected behavior and why naive logic may fail.
Lite-mode writing target:
- Write 1~2 observations that shrink the search space.
- Name one final algorithm and state target complexity explicitly.
- Validate with at least 2 edge cases and one hand simulation.
Constraints
- •n,q <= 2e5
Analysis
Key Insight
Old version remains immutable. This step should reduce search space or formalize correctness. State why this insight changes your algorithm choice.
persistent-segment-treeorder-statisticsoffline