hash table 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.
Pattern brief
Recognize first
Check if the candidate correctly uses hash tables for efficient frequency management.
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 handle cases where a number's frequency drops to zero after a delete operation.
Recognition signals
- Check if the candidate correctly uses hash tables for efficient frequency management.
- Evaluate the approach for handling multiple operations efficiently under large constraints.
Solve flow
- 1. Define the active state/window.
- 2. Update state while preserving invariants.
- 3. Validate with edge-heavy examples.
Common misses
- Failing to handle cases where a number's frequency drops to zero after a delete operation.
Recommended Ladder
Problem bank
hash table plus design pattern bank
Start by scanning with search or difficulty filters, then narrow by linked topics. The bank continues loading inside its own container so the page stays readable.
Progressive pattern bank
Use it to build pattern understanding first, then expand into the full corpus.
Showing 1 / 1 problems
Continue by topic
Once the pattern itself feels familiar, move back into concrete topic hubs so you can separate the pattern from the changing problem context.
Guided Practice Path
AI recommends problems by your level and tracks your progress.
Start Guided Patharrow_forward