using System;

​

public class Program

{

    public static void Main()

    {

        var matrix = new int[,]{ {1,2,3,4},{5,6,7,8}, {9,10,11,12}};

        // ClockwiseRotate90Degree

        var res = MatrixRotation.ClockwiseRotate90Degree(matrix);

    }

}

​

    public class MatrixRotation

    {

        public static T[,] HorizontalFlip<T>(T[,] source)

        {

            //scan col by col, reverse each column

            for (var i = 0; i < source.GetLength(1); i++)

            {

                int t = 0, b = source.GetLength(0) - 1;

                while (t < b)

                {

                    var x = source[t, i];

                    source[t, i] = source[b, i];

                    source[b, i] = x;

                    t++;b--; // don't forget to change loop variable

                }

            }

​

            return source;

        }

​

        public static T[,] VerticalFlip<T>(T[,] source)

        {

            //scan row by row, reverse each row

            for (var i = 0; i < source.GetLength(0); i++)

            {

                int l = 0, r = source.GetLength(1) - 1;

                while (l < r)

                {

                    var t = source[i, l];

                    source[i, l] = source[i, r];

                    source[i, r] = t;

                    l++;r--;

                }

            }

            return source;

        }

​

        public static T[,] SquareDiagnoalFlip<T>(T[,] source)

        {

            // main diagonal = clockwise rotate + vertical flip

            // top left to bottom right

​

            int rows = source.GetLength(0);

            int cols = source.GetLength(1);

            if (rows != cols) throw new InvalidOperationException("Cannot use this algorithm to flip rectangle, must be square!");

​

            for (var i = 0; i < rows; i++)

            {

                for (var j = 0; j <= i; j++)

                {

                    var x = source[i, j];

                    source[i, j] = source[j, i];

                    source[j, i] = x;

                }

            }

​

            return source;

        }

​

        ///

        public static T[,] DiagnoalFlip<T>(T[,] source)

        {

            // main diagonal 

            // top left to bottom right

            var res = new T[source.GetLength(1), source.GetLength(0)];

​

            // scan left side main diagnoal, swap with right side

            for (var i = 0; i < source.GetLength(0); i++)

            {

                for (var j = 0; j < source.GetLength(1); j++)

                {

                    res[j, i] = source[i, j];

                }

            }

​

            return res;

        }

​

        public static T[,] AntiDiagnoalFlip<T>(T[,] source)

        {

            // minor diagnoal or antidiagnoal,for a square it equivalent to clockwise rotate + horizontal flip

            // bottom left to top right

            int rows = source.GetLength(0);

            int cols = source.GetLength(1);

            var res = new T[cols, rows];

​

            for (var i = 0; i < rows; i++)

            {

                for (var j = 0; j < cols; j++)

                {

                    res[cols - j, rows - i] = source[i, j];

                }

            }

​

            return source;

        }

        public static T[,] ClockwiseRotate90Degree<T>(T[,] source)

        {

            // horizontal flip + diagnoal flip

            // or vertical flip + anti-diagnoal flip

            var res = HorizontalFlip(source);

            res = DiagnoalFlip(res);

            return res;

        }

        public static T[,] CounterClockwiseRotate90Degree<T>(T[,] source)

        {

            // vertical flip + diagnoal flip

​

            var res = VerticalFlip(source);

            res = DiagnoalFlip(source);

            return res;

        }

    }