array reduce transformation core interview pattern Pattern
1 problems
Pattern pages help build reusable solving frames. Identify signals first, then explain state, transition, and edge handling.
Recognition Signals
- Look for understanding of sequential operations and the effect of passing intermediate results to the reducer function.
- Test if the candidate accounts for edge cases like empty arrays properly.
Solve Flow
- 1. Define the active state/window.
- 2. Update state while preserving invariants.
- 3. Validate with edge-heavy examples.
Common Misses
- Forgetting to handle empty arrays and returning the correct initial value.