Problem #PRU-100663

Problems Methods Invariants and semi-invariants Invariants

Problem

Nine lightbulbs are arranged in a \(3 \times 3\) square. Some are on, some are off. You are allowed to change the state of all the bulbs in a column or in a row. That means all the bulbs in that row or column that were off light up and the ones that were on go dark. Is it possible to go from the arrangement in the left to the one on the right by repeating this operation?