Two prisoners, a chessboard, 64 coins and one secret square. Can a single flipped coin always reveal which square was chosen?
Two prisoners, 64 coins and a secret square
Riddle statement
Two prisoners are allowed to agree on a strategy beforehand.
Then the first prisoner enters a room with a chessboard. On each of the 64 squares there is one coin, showing either heads or tails. The guard secretly designates one square as the target.
The first prisoner may flip exactly one coin, then leaves.
The second prisoner then enters, sees the resulting board, and must identify the target square.
Can the prisoners choose a strategy that always works?