source: ip/src/main/java/geniusweb/ip/general/RandomPermutation.java@ 52

package geniusweb.ip.general;

import java.util.Random;

public class RandomPermutation {

        private int n;
        private int[] availableNumbersToChooseFrom;

        public RandomPermutation(int n) {
                this.n = n;
                this.availableNumbersToChooseFrom = new int[n];
        }

        // random permutation of numbers (1, ..., n)
        public int[] get() {
                Random randomGenerator = new Random();
                for (int i = n - 1; i >= 0; i--) {
                        availableNumbersToChooseFrom[i] = i;
                }
                int[] permutation = new int[n];
                for (int i = n - 1; i >= 0; i--) {
                        int j = randomGenerator.nextInt(i + 1);
                        permutation[i] = availableNumbersToChooseFrom[j] + 1;
                        availableNumbersToChooseFrom[j] = availableNumbersToChooseFrom[i];
                }
                return permutation;
        }
}