The warden will release the 7 prisoners to be hang on
everyday next week if they can mark their hats with a
number card from a playing card deck so that anyone may
see and guess right the others prisoner's day and time
of executions.
The cards shall be erected on hat through a small
straight cut on top.
The schedule will be randomly drawn for everyone.
No prisoner must tell his scheduled day (Sun,Mon..Sat)
and hour of execution (1:00,2:00,3:00 ... 12:00).
Since these prisoners had freed themselves a couple
of times on this same prison it should not be hard for
them to agree on a plan.
What code strategy works for them?