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In combinatorics, a matroid embedding is a set system (''F'', ''E''), where ''F'' is a collection of ''feasible sets'', that satisfies the following properties: # (''Accessibility Property'') Every non-empty feasible set ''X'' contains an element ''x'' such that ''X''\ is feasible; # (''Extensibility Property'') For every feasible subset ''X'' of a ''basis'' (''i.e.'', maximal feasible set) ''B'', some element in ''B'' but not in ''X'' belongs to the extension ext(''X'') of ''X'', or the set of all elements ''e'' not in ''X'' such that ''X''∪ is feasible; # (''Closure-Congruence Property'') For every superset ''A'' of a feasible set ''X'' disjoint from ext(''X''), ''A''∪ is contained in some feasible set for either all or no ''e'' in ext(''X''); # The collection of all subsets of feasible sets forms a matroid. Matroid embedding was introduced by Helman ''et al.'' in 1993 to characterize problems that can be optimized by a greedy algorithm. == References == * 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Matroid embedding」の詳細全文を読む スポンサード リンク
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