CustomCC0-1.0#ct-p5-032250
Versioned String Frequency
Summary
- •Phase 5 / string-advanced
- •Reasoning-first competitive programming drill
Problem Description
Maintain versions of a string with point edits; query most frequent character in substring for any version.
How to read this problem in plain language:
- This is a Phase 5 reasoning drill focused on string-advanced.
- Typical lenses to test first: persistent-segment-tree, string, data-structure.
- Constraints reminder: n,q <= 2e5
Mini examples for mental simulation:
1) Boundary example: Version changes structure but frequencies unchanged.
2) Adversarial example: Frequency trivially 1. 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
Quantifying complexity against constraints is mandatory for selecting the final approach and rejecting brute force formally.
persistent-segment-treestringdata-structure