eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2016-06-27
29:1
29:13
10.4230/LIPIcs.CPM.2016.29
article
Optimal Prefix Free Codes with Partial Sorting
Barbay, Jérémy
We describe an algorithm computing an optimal prefix free code for n unsorted positive weights in less time than required to sort them on many large classes of instances, identified by a new measure of difficulty for this problem, the alternation alpha. This asymptotical complexity is within a constant factor of the optimal in the algebraic decision tree computational model, in the worst case over all instances of fixed size n and alternation alpha. Such results refine the state of the art complexity in the worst case over instances of size n in the same computational model, a landmark in compression and coding since 1952, by the mere combination of van Leeuwen's algorithm to compute optimal prefix free codes from sorted weights (known since 1976), with Deferred Data Structures to partially sort multisets (known since 1988).
https://drops.dagstuhl.de/storage/00lipics/lipics-vol054-cpm2016/LIPIcs.CPM.2016.29/LIPIcs.CPM.2016.29.pdf
Deferred Data Structure
Huffman
Median
Optimal Prefix Free Codes
van Leeuwen.