送交者: yunle 2004年11月02日13:31:15 於 [靈機一動]http://www.bbsland.com

A set of six bank robbers decided to store their loot from a
successful job in a safe (how original…) until it was safe
(no pun intended…) to start spending the money. Being somewhat
but not completely trustful of one another, they decided to be
able to open the safe when and only when a majority (4 or more)
of the robbers was present. Therefore, the safe was provided with
a number of different locks (the key to any one not being able
to open any other), and each robber was given keys to some of
the locks. How many locks were required, and how many keys had
to be given to any one bank robber?