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Graph TheorySuperchallengeDirected Graphs and Network Flows

Directed Graphs and Network Flows · Superchallenge problem

Six teams 1,…,61,\dots,6 play a round robin where team ii beats team jj for every pair i<ji<j, EXCEPT that team 66 beats team 11, and team 55 beats team 22 (two upsets). A Hamiltonian path visits every team exactly once, always moving winner-to-loser. How many different Hamiltonian paths does this tournament have?