array plus design 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.

database4 problemstune0/4/0 difficulty mixcategory6 linked topics

Pattern brief

Recognize first

Look for understanding of iterator design patterns and the need for efficient caching.

Solve rhythm

State the active state and invariant first, explain how each update preserves them, then pressure-test with counterexamples.

Most common miss

Failing to properly cache the next element, leading to incorrect results from peek().

Recognition signals

Look for understanding of iterator design patterns and the need for efficient caching.
Test the candidate's ability to handle edge cases like empty or fully traversed iterators.
Can the candidate suggest a more efficient solution than brute force?

Solve flow

1. Define the active state/window.
2. Update state while preserving invariants.
3. Validate with edge-heavy examples.

Common misses

Failing to properly cache the next element, leading to incorrect results from peek().
Not recognizing that a brute force solution may be too slow for large inputs.
Trying to expand the full sequence causing memory issues.

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