Matrix rotation

rotate.cpp

template<std::size_t N>
void rotate_out_of_place(std::size_t (&matrix) [N][N])
{
	std::size_t copy [N][N];
	
	for (std::size_t i = 0, end = N/2; i < end; ++i)
	{
		for (std::size_t j = 0; j < N; ++j)
		{
			copy[i][j] = matrix[j][N - 1];
			
			copy[N - 1 - i][j] = matrix[j][i];
			
			copy[j][i] = matrix[i][N - 1 - j];
			
			copy[j][N - 1 - i] = matrix[N - 1 - i][N - 1 - j];
		}
	}
	
	if (N % 2) copy[N/2][N/2] = matrix[N/2][N/2];
	
	for (std::size_t i = 0; i < N; ++i)
	{
		for (std::size_t j = 0; j < N; ++j)
		{
			matrix[i][j] = copy[i][j];
		}
	}
}

template<std::size_t N>
void rotate(std::size_t (&matrix) [N][N], std::size_t i, std::size_t j)
{
	std::size_t temp = matrix[i][j];
	
	matrix[i][j] = matrix[j][N - 1];
	
	matrix[j][N - 1 - i] = matrix[N - 1 - i][N - 1 - j];
	
	matrix[N - 1 - i][N - 1 - j] = matrix[N - 1 - j][i];
	
	matrix[N - 1 - j][i] = temp;
}

template<std::size_t N>
void rotate_in_place(std::size_t (&matrix) [N][N])
{
	for (std::size_t i = 0, i_end = std::ceil(N/2.0); i < i_end; ++i)
	{
		for (std::size_t j = i, j_end = N - i; j < j_end; ++j)
		{
			rotate(matrix, i, j);
		}
	}
}