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Igor Stassiy

Publications and source records attributed to Igor Stassiy.

2 recordsLinked to original sources

A note on the Minimum Norm Point algorithm

We present a provably more efficient implementation of the Minimum Norm Point Algorithm conceived by Fujishige than the one presented in \cite{FUJI06}. The algorithm solves the minimization problem for a class of functions known as submodular. Many important functions, such as minimum cut in the graph, have the so called submodular property \cite{FUJI82}. It is known that the problem can also be efficiently solved in strongly polynomial time \cite{IWAT01}, however known theoretical bounds are far from being practical. We present an improved implementation of the algorithm, for which unfortunately no worst case bounds are know, but which performs very well in practice. With the modifications presented, the algorithm performs an order of magnitude faster for certain submodular functions.

cs.DS

Analysis of String Sorting using Heapsort

In this master thesis we analyze the complexity of sorting a set of strings. It was shown that the complexity of sorting strings can be naturally expressed in terms of the prefix trie induced by the set of strings. The model of computation takes into account symbol comparisons and not just comparisons between the strings. The analysis of upper and lower bounds for some classical algorithms such as Quicksort and Mergesort in terms of such a model was shown. Here we extend the analysis to another classical algorithm - Heapsort. We also give analysis for the version of the algorithm that uses Binomial heaps as a heap implementation.

cs.DS