array plus rolling hash 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
Looking for subarrays matching a sequence of relative comparisons, not exact values.
Solve rhythm
State the active state and invariant first, explain how each update preserves them, then pressure-test with counterexamples.
Most common miss
Forgetting that subarray length is pattern length plus one, leading to index errors.
Recognition signals
- Looking for subarrays matching a sequence of relative comparisons, not exact values.
- Hinting to consider pattern length and efficient checking, possibly via rolling hash.
- Tests the candidate's ability to transform arrays efficiently.
Solve flow
- 1. Define the active state/window.
- 2. Update state while preserving invariants.
- 3. Validate with edge-heavy examples.
Common misses
- Forgetting that subarray length is pattern length plus one, leading to index errors.
- Incorrectly transforming the array `nums` into `nums2` based on relative comparisons.
Recommended Ladder
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