Invariants & Monovariants · Difficulty 7/10 · ~45 min
Invariants & Monovariants
- Identify invariants of a process
- Use parity and coloring arguments
- Deploy monovariants for termination
Welcome to olympiad thinking. A process runs — chips move, numbers merge, signs flip — and you're asked what final states are possible. The professional move is to stop watching the motion and find what *doesn't* move: an invariant. If the target state has the wrong invariant value, no sequence of moves will ever reach it. Impossibility, proved in two lines.