How to Rotate a 2D Array of Integers

Question

I am programming a Tetris clone and in my game I store my tetromino blocks as 4x4 arrays of blocks. I now need to be able to rotate the integer positions in the arrays so that I get a rotated tetris block. I cannot simply rotate the texture because all my collision detection, etc has been designed to work with the 2D array. The game is written in C# using XNA.

How can i possibly rotate my 2D array of ints by 90 degrees clockwise/counter clockwise.

Here is how my 'L' block is stored as an example.

0 1 0 0
0 1 0 0
0 1 1 0 
0 0 0 0

Thanks for your help.

Answer 1

If they're a 2D array, you can implement rotation by copying with different array access orders.

i.e., for a clockwise rotation, try:

int [,] newArray = new int[4,4];

for (int i=3;i>=0;--i)
{
    for (int j=0;j<4;++j)
    {
         newArray[j,3-i] = array[i,j];
    }
}

Counter-clockwise is similar.

Answer 2

Don't rotate the pieces with code. Just store an array of the different piece orientations and cycle through them when the piece is rotated. There's no need to dynamically rotate them in a Tetris game.

As the problem domain is Tetris, you will find that a rotation algorithm causes undesirable effects, such as the long thin Tetronimo not alternating between two positions (as it does in the real thing).