Friendly influences, experimentally "see if it is true"
program:

Write a program which takes a friendship graph and initial state as input.
It runs the phone call pattern for each day and prints the affiliations that 
result, continuing until the pattern of affiliations on a given day matches 
a previous pattern.  Input is the number n of people in the town followed by 
n lines showing the friendships, followed by an n character line indicating 
the affiliations.  The people are identified by the numbers 1..n. 

Sample input

6
1: 2
2: 1 3 4
3: 2
4: 2
5: 6
6: 5
RDRDDD

Sample output

DRDDDD
RDRRDD
DRDDDD


Reference: Peter Winkler, "Puzzled, Delightful Graph Theory", Communications of the ACM, August 2008, Vol 51, No 8, pg 104.