CustomCC0-1.0#cp015-5122300
Increasing Subarrays with K Changes
Summary
- •Phase 5 / segment tree, binary search
- •Reasoning-first competitive programming drill
Problem Description
Given an array of n integers and q queries, each query gives l, r, k. Find the length of the longest increasing subarray in [l,r], changing at most k elements to any value.
How to read this problem in plain language:
- This is a Phase 5 reasoning drill focused on segment tree, binary search.
- Typical lenses to test first: segment tree, queries, two pointers.
- Constraints reminder: 1 <= n, q <= 10^5, 1 <= ai <= 10^9, 0 <= k <= r-l+1
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, q <= 10^5, 1 <= ai <= 10^9, 0 <= k <= r-l+1
Analysis
Key Insight
The goal is to force explicit intermediate reasoning before revealing more.
segment treequeriestwo pointers