Create 2 array with same length and same values but in different order

Question

I begin with java and I hit a problem

I need to create 2 array with the same random value but these values have to be in different order, like this:

int[] firstArray= {5, 12, 7, 10, 6, 8};
int[] secondArray= {12, 7, 8, 5, 10, 6};

But I want this with random numbers. How can I do this ? Thanks

read this one http://stackoverflow.com/questions/1519736/random-shuffling-of-an-array — Madhawa Priyashantha, Sep 07 '15 at 16:32
So what exactly is the problem? Creating the first array of random numbers, or shuffling the second one? — Mureinik, Sep 07 '15 at 16:34
See this answer: http://stackoverflow.com/a/18456998/5260943 — Arjun Panickssery, Sep 07 '15 at 16:34
@Simon M. I have a simpler solution, you don't even need to shuffle. — user3437460, Sep 07 '15 at 17:14

score 1 · Answer 1 · answered Sep 07 '15 at 16:38

1

There's a library provided shuffle method you can use, in case you don't want to define your own.

String[] alpha = { "A", "E", "I", "O", "U" };
List list = new ArrayList(alpha);
Collections.shuffle(list);
String[] shuffledAlpha = list.toArray();

answered Sep 07 '15 at 16:38

Raman Shrivastava

2,923
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Michele Lacorte · Answer 2 · 2015-09-07T16:53:26.560

Try this

public static int[] RandArray(int[] array){
    Random rand = new Random();         

    for (int i=0; i<array.length; i++) {
        int randomPosition = rand.nextInt(array.length);
        int temp = array[i];
        array[i] = array[randomPosition];
        array[randomPosition] = temp;
    }

    return array;
}

In the main add this

int[] firstArray = {5, 12, 7, 10, 6, 8};
int[] secondArray = RandArray(firstArray);
    for (int i = 0; i < secondArray.length; i++)
    {
      System.out.print(secondArray[i] + " ");
    }
    System.out.println();

and this is output:

7 8 10 6 12 5

To randomize firstArray add this code:

public static int[] RandFirstArray(int arraySize, int min, int max){
    Random rand = new Random();         
     int[] firstArray = new int[arraySize];
    for (int i=0; i<arraySize; i++) {
        firstArray[i] = rand.nextInt((max - min) + 1) + min;
    }
    return firstArray;
}

Than in the main:

    //Use RandFirstArray(ArrayLength, MinValue, MaxValue)
    int[] firstArray = RandFirstArray(6, 0 , 20);
    System.out.println("First Array\n");
    for (int i = 0; i < firstArray.length; i++)
    {
      System.out.print(firstArray[i] + " ");
    }
    System.out.println("\n\nSecond Array\n");
    int[] secondArray = RandArray(firstArray);
    for (int i = 0; i < secondArray.length; i++)
    {
      System.out.print(secondArray[i] + " ");
    }
    System.out.println();

New output:

First Array

3 20 5 13 8 11

Second Array

8 13 11 20 3 5

It will not create a new array it will modify the given array. — Sanjeev Kumar, Sep 07 '15 at 16:37
It creates the array equal to the first with the changed values of position .. is what he wants! — Michele Lacorte, Sep 07 '15 at 16:38
have you read the code? int[] secondArray = RandArray(firstArray); it create secondArray... — Michele Lacorte, Sep 07 '15 at 16:41
Thanks! And is that possible that the first array has random values? — Simon M., Sep 07 '15 at 16:42

score 0 · Answer 3 · edited May 23 '17 at 10:26

Use this method, using a Fisher-Yates shuffle.

Fisher Yates shuffle

Algorithm

public int[] shuffleArray(int[] array)
{
    int index;
    Random random = new Random();
    for (int i = array.length - 1; i > 0; i--)
    {
        index = random.nextInt(i + 1);
        if (index != i)
        {
            array[index] ^= array[i];
            array[i] ^= array[index];
            array[index] ^= array[i];
        }
    }
    return array;
}

Create 2 array with same length and same values but in different order

3 Answers3