An analysis of algorithms for the Dutch National Flag Problem
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.