Round-Robin

Round-robin means every team / player / participant in a tournament or league plays every other participant the same number of times. Single round-robin: each pair plays once, requiring n(n-1)/2 matches for n teams. Double round-robin: each pair plays twice (home–away), requiring n(n-1) matches. It's the foundational structure of league scheduling math; the Berger table is the oldest closed-form solution. Beyond sports leagues, the round-robin structure also appears in competition types (game tournaments, dance contests, lecture competitions) and even in software test suites. With the round-robin constraint, soft objectives like break minimization, distance optimization, and broadcaster constraints are optimized on top.