Making 2d Array Java

Question

say I have a 1D array like

int[] array1d = {1,2,3}

I would like to convert it into 2D array2d[3][2] which holding 2 int that are different. E.g.:

1  2
1  3
2  3

currently I made this

int[] array1d = new int[3];
        array1d[0] = 1;
        array1d[1] = 2;
        array1d[2] = 3;

int[][] array2d = new int[3][2];

for (int i=0; i<3; i++) {
            for (int j=0; j<2; j++) {
                array2d[i][j] = array1d[j];
            }
        }

but it gives me only 1,2.

Have you thought about what kind of algorithm you want to use? Also, what if your array is 1,1,2? What if it's 1,2,3,4? — Joni
– Joni, Commented Feb 25, 2016 at 18:42
the 1d arrays I use and want to covert into 2d array contain int that are different as the second one you write 1,2,3,4 and if it like that I want the output to be 1,2 1,3 1,4 2,3 2,4 3,4 I am new to this and I can't make it — mddev
– mddev, Commented Feb 25, 2016 at 18:46

Community · Accepted Answer · 2017-04-13 12:40:36Z

1

Generally speaking, what you want is called combinations (in your example, of size 2 taken from a 3-sized array). So, order does not matter (e.g. [1, 2] equals [2, 1]).

As already specified in the comments, you should consider a more general solution and one can be found here. Besides the actual code, you will also find a code reviews from Codereview community.

edited Apr 13, 2017 at 12:40

CommunityBot

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answered Feb 25, 2016 at 18:56

Alexei - check Codidact

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Comments

Nishant Pal · Accepted Answer · 2016-02-25 20:23:58Z

0

i have done this using random numbers.try this code

` import java.util.Random;

     public final class RandomInteger {

   public static void main(String... aArgs){

    Random randomGenerator = new Random();  
    int[] array1d = new int[3];
    array1d[0] = 1;
    array1d[1] = 2;
    array1d[2] = 3;
    int[] array2d = new int[3][2];
    int randomInt;
    for (int i=0; i<3; i++) {
          for (int j=0; j<2; j++) {
              randomInt = randomGenerator.nextInt(3);
              array2d[i][j] = array1d[randomInt];
                                   }
                            }

                                              }
                                    }

`

answered Feb 25, 2016 at 20:23

Nishant Pal

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