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/*
* Copyright (c) 2003 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* -Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduct the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT
* BE LIABLE FOR ANY DAMAGES OR LIABILITIES SUFFERED BY LICENSEE AS A RESULT
* OF OR RELATING TO USE, MODIFICATION OR DISTRIBUTION OF THE SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE SOFTWARE, EVEN
* IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that Software is not designed, licensed or intended for
* use in the design, construction, operation or maintenance of any nuclear
* facility.
*/
/*
* @(#)Permuter.java 1.6 03/01/23
*/
/**
* An object that implements a cheesy pseudorandom permutation of the integers
* from zero to some user-specified value. (The permutation is a linear
* function.)
*
* @version 1.6 01/23/03
* @author Josh Bloch
*/
class Permuter {
/**
* The size of the permutation.
*/
private int modulus;
/**
* Nonnegative integer less than n that is relatively prime to m.
*/
private int multiplier;
/**
* Pseudorandom nonnegative integer less than n.
*/
private int addend = 22;
public Permuter(int n) {
if (n<0) {
throw new IllegalArgumentException();
}
modulus = n;
if (n==1) {
return;
}
// Initialize the multiplier and offset
multiplier = (int) Math.sqrt(n);
while (gcd(multiplier, n) != 1) {
if (++multiplier == n) {
multiplier = 1;
}
}
}
/**
* Returns the integer to which this permuter maps the specified integer.
* The specified integer must be between 0 and n-1, and the returned
* integer will be as well.
*/
public int map(int i) {
return (multiplier * i + addend) % modulus;
}
/**
* Calculate GCD of a and b, which are assumed to be non-negative.
*/
private static int gcd(int a, int b) {
while(b != 0) {
int tmp = a % b;
a = b;
b = tmp;
}
return a;
}
/**
* Simple test. Takes modulus on command line and prints out permutation.
*/
public static void main(String[] args) {
int modulus = Integer.parseInt(args[0]);
Permuter p = new Permuter(modulus);
for (int i=0; i<modulus; i++) {
System.out.print(p.map(i)+" ");
}
System.out.println();
}
}