rotate_4.cpp

//traverse through the layers
for(int layer=0; layer<n/2; layer++)
    {
        int first = layer;
        int last = n-layer-1;

        //traverse through start to end
        for(int i=first; i<last; i++)
        {
            //creating the offset
            int offset = i - first;

            //storing the top value
            int top = matrix[first][i];

            //store left in top
            matrix[first][i] = matrix[last-offset][first];

            //store bottom in left
            matrix[last-offset][first] = matrix[last][last-offset];

            //store right in bottom
            matrix[last][last-offset] = matrix[i][last];

            //store top in right
            matrix[i][last] = top;
        }
    }