Hard combinatorics with team nominated based on three rankings
Source: Germany 2023, Problem 3
June 16, 2023
combinatoricscombinatorics proposedgraph theoryTournamentTournament graphs
Problem Statement
For a competition a school wants to nominate a team of students, where is a given positive integer. Each member of the team has to compete in the three disciplines juggling, singing and mental arithmetic. To qualify for the team, the students of the school compete in qualifying competitions, determining a unique ranking in each of the three disciplines. The school now wants to nominate a team satisfying the following condition: If a student is not nominated for the team, there is a student on the team who defeated in at least two disciplines.Determine all positive integers such that for any combination of rankings, a team can be chosen to satisfy the condition , whena) ,
b) .