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design plus simulation 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.

database2 problemstune1/1/0 difficulty mixcategory3 linked topics

Pattern brief

Recognize first

Check if the candidate tracks slot availability correctly for each car type.

Solve rhythm

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

Most common miss

Mixing up car type indices leading to wrong counter updates.

Recognition signals

  • Check if the candidate tracks slot availability correctly for each car type.
  • Observe whether addCar updates the internal state without overwriting counts.
  • Looking for a clean approach to handle boundary conditions and direction changes.

Solve flow

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

Common misses

  • Mixing up car type indices leading to wrong counter updates.
  • Not handling the boundary conditions properly, causing the robot to move out of bounds.

Recommended Ladder

Problem bank

design plus simulation 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

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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.

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Design plus Simulation LeetCode Pattern: 2 Solutions