Output polynomial enumeration of all fixed-cardinality ideals of a poset, respectively all fixed-cardinality subtrees of a tree
Abstract
The N cardinality k ideals of any w-element poset (w, k variable) can be enumerated in time O(Nw3). The corresponding bound for k-element subtrees of a w-element tree is O(Nw5). An algorithm is described that by the use of wildcards displays all order ideals of a poset in a compact manner, i.e. not one by one.
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