array plus enumeration Pattern
Pattern hubs are for building transferable solving frames. Learn the recognition signals first, then drill state definition, update rules, and edge explanation until the pattern feels stable.
Pattern brief
Recognize first
Asks if brute-force enumeration is acceptable given small constraints.
Solve rhythm
State the active state and invariant first, explain how each update preserves them, then pressure-test with counterexamples.
Most common miss
Using <= instead of < for indices, causing duplicates or invalid triplets.
Recognition signals
- Asks if brute-force enumeration is acceptable given small constraints.
- Checks understanding of absolute difference and triplet conditions.
- Looking for awareness of pattern repetition and consecutive subarray detection.
Solve flow
- 1. Define the active state/window.
- 2. Update state while preserving invariants.
- 3. Validate with edge-heavy examples.
Common misses
- Using <= instead of < for indices, causing duplicates or invalid triplets.
- Not verifying consecutive repetitions correctly, leading to false positives.
- Forgetting the radius cutoff, leading to including towers beyond reach.
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