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In combinatorial mathematics, a partial permutation, or sequence without repetition, on a finite set S is a bijection between two specified subsets of S. That is, it is defined by two subsets U and V of equal size, and a one-to-one mapping from U to V. Equivalently, it is a partial function on S that can be extended to a permutation. [1] [2]
In combinatorics, the twelvefold way is a systematic classification of 12 related enumerative problems concerning two finite sets, which include the classical problems of counting permutations, combinations, multisets, and partitions either of a set or of a number.
In other words, a permutation class is a hereditary property of permutations, or a downset in the permutation pattern order. [1] A permutation class may also be known as a pattern class, closed class, or simply class of permutations. Every permutation class can be defined by the minimal permutations which do not lie inside it, its basis. [2]
1-planarity [1] 3-dimensional matching [2] [3]: SP1 Bandwidth problem [3]: GT40 Bipartite dimension [3]: GT18 Capacitated minimum spanning tree [3]: ND5 Route inspection problem (also called Chinese postman problem) for mixed graphs (having both directed and undirected edges). The program is solvable in polynomial time if the graph has all ...
Other properties of the Lehmer code include that the lexicographical order of the encodings of two permutations is the same as that of their sequences (σ 1, ..., σ n), that any value 0 in the code represents a right-to-left minimum in the permutation (i.e., a σ i smaller than any σ j to its right), and a value n − i at position i ...
The ! permutations of the numbers from 1 to may be placed in one-to-one correspondence with the ! numbers from 0 to ! by pairing each permutation with the sequence of numbers that count the number of positions in the permutation that are to the right of value and that contain a value less than (that is, the number of inversions for which is the ...
Such multiply transitive permutation groups can be defined for any natural number k. Specifically, a permutation group G acting on n points is k-transitive if, given two sets of points a 1, ... a k and b 1, ... b k with the property that all the a i are distinct and all the b i are distinct, there is a group element g in G which maps a i to b i ...
Namely, a Riesz group satisfies the Riesz interpolation property: if x 1, x 2, y 1, y 2 are elements of G and x i ≤ y j, then there exists z ∈ G such that x i ≤ z ≤ y j. If G and H are two partially ordered groups, a map from G to H is a morphism of partially ordered groups if it is both a group homomorphism and a monotonic function.