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  2. Exact cover - Wikipedia

    en.wikipedia.org/wiki/Exact_cover

    For example, an exact cover problem is equivalent to an exact hitting set problem, an incidence matrix, or a bipartite graph. In computer science, the exact cover problem is a decision problem to determine if an exact cover exists. The exact cover problem is NP-complete [3] and is one of Karp's 21 NP-complete problems. [4]

  3. Subset sum problem - Wikipedia

    en.wikipedia.org/wiki/Subset_sum_problem

    The subset sum problem (SSP) is a decision problem in computer science. In its most general formulation, there is a multiset S {\displaystyle S} of integers and a target-sum T {\displaystyle T} , and the question is to decide whether any subset of the integers sum to precisely T {\displaystyle T} . [ 1 ]

  4. Sum-free set - Wikipedia

    en.wikipedia.org/wiki/Sum-free_set

    For example, the set of odd numbers is a sum-free subset of the integers, and the set {N + 1, ..., 2N } forms a large sum-free subset of the set {1, ..., 2N }. Fermat's Last Theorem is the statement that, for a given integer n > 2, the set of all nonzero n th powers of the integers is a sum-free set.

  5. Subset - Wikipedia

    en.wikipedia.org/wiki/Subset

    These are two examples in which both the subset and the whole set are infinite, and the subset has the same cardinality (the concept that corresponds to size, that is, the number of elements, of a finite set) as the whole; such cases can run counter to one's initial intuition. The set of rational numbers is a proper subset of the set of real ...

  6. Naive set theory - Wikipedia

    en.wikipedia.org/wiki/Naive_set_theory

    As an illustration, let R be the set of real numbers, let Z be the set of integers, let O be the set of odd integers, and let P be the set of current or former U.S. Presidents. Then O is a subset of Z, Z is a subset of R, and (hence) O is a subset of R, where in all cases subset may even be read as proper subset. Not all sets are comparable in ...

  7. Fréchet filter - Wikipedia

    en.wikipedia.org/wiki/Fréchet_filter

    If the base set is finite, then = ℘ since every subset of , and in particular every complement, is then finite.This case is sometimes excluded by definition or else called the improper filter on . [2] Allowing to be finite creates a single exception to the Fréchet filter’s being free and non-principal since a filter on a finite set cannot be free and a non-principal filter cannot contain ...

  8. Paradoxes of set theory - Wikipedia

    en.wikipedia.org/wiki/Paradoxes_of_set_theory

    The set E of all finite definitions of real numbers is a subset of A. As A is countable, so is E. Let p be the nth decimal of the nth real number defined by the set E; we form a number N having zero for the integral part and p + 1 for the nth decimal if p is not equal either to 8 or 9, and unity if p is equal to 8 or 9.

  9. Multiple subset sum - Wikipedia

    en.wikipedia.org/wiki/Multiple_subset_sum

    The multiple subset sum problem is an optimization problem in computer science and operations research. It is a generalization of the subset sum problem . The input to the problem is a multiset S {\displaystyle S} of n integers and a positive integer m representing the number of subsets.