An analysis of algorithms for the Dutch National Flag Problem

  • Authors:
  • Colin L. McMaster

  • Affiliations:
  • Univ. of California, Berkeley

  • Venue:
  • Communications of the ACM
  • Year:
  • 1978

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Abstract

Solutions to the Dutch National Flag Problem have been given by Dijkstra [1] and Meyer [3]. Dijkstra starts with a simple program and arrives at an improved program by refinement. Both of the algorithms given by Dijkstra are shown to have an expected number of swaps which is 2/3N + &thgr;(1) and that these values differ at most by 1/3 of a swap and asymptotically by 1/4 of a swap. The algorithm of Meyer is shown to have expected swap complexity 5/9 N.