Fisher-Yates Shuffle algorithm

Description:

An algorithm for shuffling a finite sequence into randomized permutation.

Process:

Let arr be a finite sequence. Let n be the length of the finite sequence arr. 

for i from n-1 downto 1 do:

    j<- a random number which 0<=j<=i;

    swap arr[i],arr[j];

Time Complexity:

O(n) where n is length of the sequence

Code(C#):

class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("Hello World!");

            char[] c = { 'A', 'B', 'C', 'D', 'E' };

            

            Console.Write("Before:");

            PrintSequence(c);

            Console.WriteLine();

            FisherYatesShuffleFunc(ref c);

            Console.Write("After:");

            PrintSequence(c);

            Console.WriteLine();

        }

        static void FisherYatesShuffleFunc(ref char[] s)

        {

            Random r = new Random();

            for(int i=s.Length-1;i>=1;i--)

            {

                int j = r.Next(i + 1);

                char t=s[i];

                s[i] = s[j];

                s[j] = t;

            }

        }

        static void PrintSequence(char []s)

        {

            Console.Write(s);

        }

    }

e.g.

Input: arr=['A','B','C','D','E'] , n=5

(1)i=4. Let j=3;

swap arr[4] and arr[3]

result:arr=['A','B','C','E','D']

(2)i=3. Let j=1;

swap arr[3] and arr[1]

result:arr=['A','E','C','B','D']

(3)i=2. Let j=1;

swap arr[2] and arr[1]

result:arr=['A','C','E','B','D']

(4)i=1. Let j=0;

swap arr[1] and arr[0]

result:arr=['C,'A','E','B','D']

Done: output:arr=['C,'A','E','B','D']