📖Story
100 prisoners are each in isolated cells. Each day, one prisoner is randomly chosen and brought to a room with a single light bulb.
The light can be switched ON or OFF. Prisoners can't communicate in any other way. The warden will free everyone IF one prisoner can correctly declare: 'All 100 prisoners have visited this room.' If they're wrong, everyone dies. They get to plan a strategy BEFORE isolation. What do they do?