12 men and 12 women at the dance
Source: XI May Olympiad (Olimpiada de Mayo) 2005 L2 P4
September 19, 2022
combinatorics
Problem Statement
At a dance there are men, numbered to , and women numbered to . Each man is assigned a “secret friend” among the others. They all danced all the pieces. In the first piece each man danced with the woman who has the same number. From then on, each man danced the new piece with the woman who had danced the piece earlier with his secret friend. In the third piece the couples were:
https://cdn.artofproblemsolving.com/attachments/c/d/f5ea0931e5751739c1ba556f84ab5736f2d11a.png
Find the number of each man's secret friend.