create a new column core interview pattern 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
The candidate uses direct assignment to create the new column.
Solve rhythm
State the active state and invariant first, explain how each update preserves them, then pressure-test with counterexamples.
Most common miss
Incorrectly assigning the new column without ensuring it calculates the correct value.
Recognition signals
- The candidate uses direct assignment to create the new column.
- The candidate understands DataFrame manipulation with methods like `assign()` or `apply()`.
Solve flow
- 1. Define the active state/window.
- 2. Update state while preserving invariants.
- 3. Validate with edge-heavy examples.
Common misses
- Incorrectly assigning the new column without ensuring it calculates the correct value.
Recommended Ladder
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