java multi-dimensional array transposing

Question

I have a row-based multidimensional array:

/** [row][column]. */
public int[][] tiles;

I would like to transform this array to column-based

Answer 1

try this:

@Test
    public void transpose() {

        final int[][] original = new int[][] { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 } };
        for (int i = 0; i < original.length; i++) {
            for (int j = 0; j < original[i].length; j++) {
                System.out.print(original[i][j] + " ");
            }
            System.out.print("\n");
        }
        System.out.print("\n\n matrix transpose:\n");
        // transpose
        if (original.length > 0) {
            for (int i = 0; i < original[0].length; i++) {
                for (int j = 0; j < original.length; j++) {
                    System.out.print(original[j][i] + " ");
                }
                System.out.print("\n");
            }
        }
    }

output:

1 2 3 4 
5 6 7 8 
9 10 11 12 


 matrix transpose:
1 5 9 
2 6 10 
3 7 11 
4 8 12 

Answer 2

a bit more generic way:

/**
 * Transposes the given array, swapping rows with columns. The given array might contain arrays as elements that are
 * not all of the same length. The returned array will have {@code null} values at those places.
 * 
 * @param <T>
 *            the type of the array
 * 
 * @param array
 *            the array
 * 
 * @return the transposed array
 * 
 * @throws NullPointerException
 *             if the given array is {@code null}
 */
public static <T> T[][] transpose(final T[][] array) {
    Objects.requireNonNull(array);
    // get y count
    final int yCount = Arrays.stream(array).mapToInt(a -> a.length).max().orElse(0);
    final int xCount = array.length;
    final Class<?> componentType = array.getClass().getComponentType().getComponentType();
    @SuppressWarnings("unchecked")
    final T[][] newArray = (T[][]) Array.newInstance(componentType, yCount, xCount);
    for (int x = 0; x < xCount; x++) {
        for (int y = 0; y < yCount; y++) {
            if (array[x] == null || y >= array[x].length) break;
            newArray[y][x] = array[x][y];
        }
    }
    return newArray;
}

Answer 3

I´m just digging this thread up because i did not find a working solution in the answers, therefore i will post one to help anyone who searches for one:

public int[][] transpose (int[][] array) {
  if (array == null || array.length == 0)//empty or unset array, nothing do to here
    return array;

  int width = array.length;
  int height = array[0].length;

  int[][] array_new = new int[height][width];

  for (int x = 0; x < width; x++) {
    for (int y = 0; y < height; y++) {
      array_new[y][x] = array[x][y];
    }
  }
  return array_new;
}

you should call it for example via:

int[][] a = new int[][] {{1,2,3,4},{5,6,7,8}};
for (int i = 0; i < a.length; i++) {
  System.out.print("[");
  for (int y = 0; y < a[0].length; y++) {
    System.out.print(a[i][y] + ",");
  }
  System.out.print("]\n");
}

a = transpose(a); // call
System.out.println("");

for (int i = 0; i < a.length; i++) {
  System.out.print("[");
  for (int y = 0; y < a[0].length; y++) {
    System.out.print(a[i][y] + ",");
  }
  System.out.print("]\n");
} 

which will as expected output:

[1,2,3,4,]
[5,6,7,8,]

[1,5,]
[2,6,]
[3,7,]
[4,8,]

Answer 4

       public int[][] getTranspose() {
            int[][] transpose = new int[row][column];
            for (int i = 0; i < row; i++) {
                for (int j = 0; j < column; j++) {
                    transpose[i][j] = original[j][i];
                }
            }
            return transpose;
        }

Answer 5

import java.util.*;

public class TestClass {

    public static void main(String args[] ) throws Exception {

        Scanner in=new Scanner(System.in);

        int isize=in.nextInt();
        int jsize=in.nextInt();
        int arr[][]=new int[isize][jsize];
        int array[][]=new int[jsize][isize];
        for(int i=0;i<isize;i++) {
            for(int j=0;j<jsize;j++) {
                arr[i][j]=in.nextInt();
            }
            System.out.println("\n");
        }

        for(int n=0;n<arr[0].length;n++) {
            for(int m=0;m<arr.length;m++) {
                array[n][m]=arr[m][n];
                System.out.print(array[n][m]+" ");
            }
            System.out.print("\n");
        }
    }
}