On the Stack Sortable and Pushpopable Permutations
نویسندگان
چکیده
This work proposes an O(log n) time parallel algorithm for testing whether a permutation is stack sortable or not by O(n) processors under the PRAM EREW computational model. Additionally, the number of permutations which are both stack sortable and pushpopable is also discussed, and an equality is finally obtained, which combines n!, 2, Cn, and Un together where Cn is the Catalan number and Un is the number of permutations which are both stack unsortable and unpushpopable. Keyword: Permutations, stack sortable permutations, inverse permutations, inversion tables, involution permutations, Catalan numbers.
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