In a top security prison, BigBang, there is a tradition that any inmate can obtain freedom by passing through a 100m-long corridor without being caught by a blind guard. The corridor has nine 10m-long perpendicular branches on one side at every 10m and is so narrow, that only one person can pass at a time.
The inmate and the guard start walking toward each other from the opposite ends of the corridor at the same time. The guard may decide to check any of the side branches. The only rule is that the inmate has to maintain the same speed as the guard's at every moment.
Is it possible to get lucky and escape from BigBang?
Prisoner _|_|_|_|_|_|_|_|_|_ Guard
(In reply to
solution by Charlie)
This solution assumes the prisoner can't/won't change direction. If the prisoner arrives at an intersection, goes north HALF the way, and then goes south, he will "change parity", and thus he might escape.
re: solution -- an objection
