Mathematical insight: parity, invariants, closed forms
- Stage
- 4
- Module
- M4.5
- Lessons
- 1
In this module
- Recognize invariants that remain unchanged through a process.
- Determine whether a state is reachable by analyzing parity and conservation laws.
- Derive closed-form solutions instead of simulating step by step.
- Use mathematical reasoning to prune impossible branches early.
Before this module
Lessons
Practice
Try these on the judges. Each link opens the problem on WMOJ or DMOJ.
- 2018 S1Voronoi Villages (opens on DMOJ in a new tab) DMOJ
Determine if a sequence of swaps can reach a target arrangement.
Why DMOJ: An invariant determines reachability without simulation.
- 2022 J5Square Pool (opens on WMOJ in a new tab) WMOJ
Find the total cost after many operations by discovering a pattern.
Why DMOJ: Closed-form formula avoids step-by-step simulation.