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

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,]