Sorting Multisets Stably in Minimum Space

Abstract. In a decision tree model, (n log2 n m i=1 ni log2 ni + n) is known to be a lower bound for sorting a multiset of size n containing m distinct elements, where the ith distinct element appears ni times. We present a minimum space algorithm that sorts stably a multiset in asymptotically optimal worst-case time. A Quicksort type approach is used, where at each recursive step the median is chosen as the partitioning element. To obtain a stable minimum space implemention, we develop linear-time in-place algorithms for the following problems, which have interest of their own: Stable unpartitioning: Assume that an n-element array A is stably parti

• Type: Conference
• Year: 1992
• Where: SWAT
• Authors: Jyrki Katajainen, Tomi Pasanen
• Keywords: Algorithms, Distinct Element, Element Appears Ni, Minimum Space, SWAT 1992