Suppose there were three events that could be done in any order. Let these events be A, B and C. There are a total of 6 possible ways the events can be performed.

However, this time, there is a restriction. B can only be performed after A. In other words, A must be performed before B can, and ACB is also accepted.

Your task is to find a general formula for X number of events, and Y number of restrictions.

None of the events is mentioned in more than one restriction.

Since events appear at most in one restriction...

Each restriction halves the possible solutions, so the answer is X!/2^Y.

The maximum number of restrictions is X/2.
Edited on February 10, 2005, 2:33 pm

Posted by e.g. on 2005-02-10 14:32:15