Array Rotating的解题

Questions:

1. to clockwise, or to counter-clockwise?

2. is it required to rotate the array in-place or allowed to copy to a new array?

Logic:

1. Rotate Layer-by-layer.

2. In each layer, rotate element-by-element. 

3. We need a extra variable to save the previous value.

Source codes:

void Rotate(int [][] arr, int N)
{
  for (int layer=0; layer < N/2; layer++)
  {
    first = layer;
    last = N - layer;
    for (int pos = first; pos < last; pos++)
    {
      //offset is calculated from the back
      offset = pos - first;
      //copy top left
      top = arr[first][pos];
      //then copy bottom left to top left
      arr[first][pos] = arr[last-offset][first];
      //then copy bottom right to bottom left
      arr[last-offset][first] = arr[last][last-offset];
      //then copy top right to bottom right
      arr[last][last-offset] = arr[pos][last];
      //finally copy saved top left to top right
      arr[pos][last] = top;   
    }
  }
  return;
}