Rotating a matrix

[Piet Souris]

I was doing some exercise where I frequently needed to rotate or flip a 2D rectangular array (matrix).

Now, one way to do such thing is to have two nested loops, and swap the corresponding elements. But that means what I call 'a lot of index juggling'.

Suppose we have the methods 'int[] getColumn(int[][] array, int column)' and 'int[] reverse(int[] array)'.

When we rotate a matrix right, then we see that column 0 becomes row 0, albeit reversed. So our method can become:

public static int[][] rotateRight(int[][] array) {
    return IntStream.range(0, array[0].length)
        .mapToObj(i -> reverse(getCol(array, i)))
        .toArray(int[][]::new)
    ;
}

Can you find similar methods for rotating left and flipping horizontally or vertically?