Z78UkQc8

1package common;
2
3/**
4 *
5 * @author Joseph Short <Joseph.J.Short at gmail.com>
6 */
7public class PermutationSet {
8
9    private byte[] selection;
10    private byte choose;
11    private int totalPermutations;
12    private byte[][] permutations;
13    private int c = 0;
14
15    public PermutationSet(byte[] selection, byte choose) {
16        this.selection = new byte[selection.length];
17        this.choose = choose;
18        System.arraycopy(selection, 0, this.selection, 0, selection.length);
19        totalPermutations = (int) (Maths.factorial(selection.length)
20                / Maths.factorial(selection.length - choose));
21        permutations = new byte[totalPermutations][choose];
22
23        byte[] permutation = new byte[choose];
24        boolean[] allocation = new boolean[selection.length];
25        seek(permutation, allocation, 0);
26    }
27
28    private void seek(byte[] permutation, boolean[] allocation, int p) {
29        if (p == choose) {
30            System.arraycopy(permutation, 0, permutations[c], 0, choose);
31            c++;
32        } else {
33            for (byte i = 0; i < selection.length; i++) {
34                if (!allocation[i]) {
35                    allocation[i] = true;
36                    permutation[p] = selection[i];
37                    seek(permutation, allocation, p + 1);
38                    allocation[i] = false;
39                }
40            }
41        }
42    }
43
44    public long getTotalPermutations() {
45        return totalPermutations;
46    }
47
48    public String getPermutationAsString(int i) {
49        String result = "";
50        for (byte digit : permutations[i]) {
51            result += digit;
52
53        }
54        return result;
55    }
56
57    public byte[] getPermutation(int i) {
58        byte[] permutation = new byte[choose];
59        System.arraycopy(permutations[i], 0, permutation, 0, choose);
60        return permutation;
61    }
62}