This tag is for questions asking for combinatorial structures of maximum or minimum possible size under some constraints. Typical questions ask for bounds or the exact value of the extremal size, or for the structure of extremal configurations.

Examples include maximum cliques or independent sets in graphs, the largest possible family of subsets of a given set such that any two of them intersect, the minimum size of a set of lotto bets guaranteeing winning a price in a certain category, etc.

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