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finally... amogus

Source: Canada Repechage 2022/1 CMOQR

March 19, 2022
graph theoryCanadarepechage

Problem Statement

Let n2n \geq 2 be a positive integer. On a spaceship, there are nn crewmates. At most one accusation of being an imposter can occur from one crewmate to another crewmate. Multiple accusations are thrown, with the following properties: • Each crewmate made a different number of accusations. • Each crewmate received a different number of accusations. • A crewmate does not accuse themself. Prove that no two crewmates made accusations at each other.