CustomCC0-1.0#cpq0101400
Interleaved Segment Sums
Summary
- •Phase 6 / prefix-sum/queries
- •Reasoning-first competitive programming drill
Problem Description
Given an array of n integers and q queries, each query gives two indices l and r (1 ≤ ). For each query, compute the sum of all array elements in positions with the same parity as l between l and r.
How to read this problem in plain language:
- This is a Phase 6 reasoning drill focused on prefix-sum/queries.
- Typical lenses to test first: prefix-sum, queries, array.
- Constraints reminder: 1 ≤ n,
Mini examples for mental simulation:
1) Boundary example: Describe why this case is tricky. Explain expected behavior and why naive logic may fail.
2) Adversarial example: Adversarial case where naive greedy/local decision looks correct but fails globally.
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
- •1 ≤ n,
Analysis
Key Insight
Use this hint to refine your reasoning. This step should reduce search space or formalize correctness. State why this insight changes your algorithm choice.
prefix-sumqueriesarray