get Permutations for List of int array - Java java.lang

Java examples for java.lang:int Array

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Description

get Permutations for List of int array

Demo Code


import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main{
    public static void main(String[] argv) throws Exception{
        int number = 2;
        System.out.println(java.util.Arrays.toString(getPermutations(number)));
    }/*w ww  . j  a v a  2s. c  o m*/
    public static List<int[]> getPermutations(int number) {
        List<int[]> allPermutations = new ArrayList<int[]>();
        int[] inputNumbers = new int[number];
        for (int i = 0; i < number; i++)
            inputNumbers[i] = i;
        listAllPermutations(allPermutations, inputNumbers);
        return allPermutations;

    }
    private static void listAllPermutations(List<int[]> allPermutations,
            int[] inputNumbers) {
        int emptyArray[] = new int[0];
        computePermutations(allPermutations, emptyArray, inputNumbers);

    }
    private static void computePermutations(List<int[]> allPermutations,
            int[] fixed, int[] variablePool) {
        int n = variablePool.length;
        if (n == 0)
            allPermutations.add(fixed);
        else {
            for (int i = 0; i < n; i++) {
                int fixed2[] = Arrays.copyOf(fixed, fixed.length + 1);
                fixed2[fixed.length] = variablePool[i];
                int variablePool2[] = new int[n - 1];
                int t = 0;
                for (int j = 0; j < n; j++) {
                    if (j != i)
                        variablePool2[t++] = variablePool[j];
                }
                computePermutations(allPermutations, fixed2, variablePool2);
            }
        }
    }
}

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