A and B are prisoners. The jailer have them play a game. He places one coin on each cell of an 8x8 chessboard. Some are tails up and others are heads up. B cannot yet see the board. The jailer shows the board to A and selects a cell. He will allow A to flip exactly one coin on the board. Then B arrives. He is asked to inspect the board and then guess the cell selected by the jailer. If B guesses the correct cell among 64 options, A and B are set free. Otherwise, they are both executed. Is there a winning strategy for A and B? (They can co-operate and discuss a strategy before the game starts).
- via Algorithmic puzzles