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From: posert@ics.uci.edu (Bob Posert)
Newsgroups: comp.sources.wanted,alt.msdos.programmer
Subject: Re: Need algorithm to scramble order of array
Summary: O(n) algorithm
Message-ID: <14831@paris.ics.uci.edu>
Date: 17 May 89 18:26:38 GMT
References: <3008@cps3xx.UUCP>
Sender: news@paris.ics.uci.edu
Reply-To: Bob Posert <posert@ics.uci.edu>
Organization: University of California, Irvine - Dept of ICS
Lines: 21

In article <3008@cps3xx.UUCP> reedp@frith.egr.msu.edu () writes:
>I need a fast algorithm to randomly rearrange the order of elements in
>an array.  [...]
>	n = size of array


The algorithm I usually use is:

	{Get all numbers in the array}
	for i = 1 to N do
		a[i] = i
	endfor

	{Scramble them}
	for i = 1 to N do
		j = { random number, 1 <= j <= N }
		swap(a[i], a[j]);
	endfor
--
Bob Posert
I'm: posert@bonnie.ics.uci.edu or {sdcsvax|ucbvax}!ucivax!bonnie!posert