Randomise character positions in string

[Mike P]

Does anybody have a simple method for randomising the character
positions in a string?

 

[Roger Frost]

Like a scramble method where "Hello, World!" becomes something like
"leol,H!o rlWd" ?

 

[Marc Gravell]

How about (off the top of my head):

public static string Scramble(string input) {
if(string.IsNullOrEmpty(input)) return input; // GIGO

List<char> inputChars = new List<char>(input);
char[] outputChars = new char[inputChars.Count];
Random rand = new Random();
// fill backwards to simplify Rand.Next() logic
for (int i = inputChars.Count - 1; i >= 0; i--)
{
int index = rand.Next(i);
outputChars = inputChars[index];
inputChars.RemoveAt(index);
}
return new string(outputChars);
}

public static void Main()
{
string foo = "The quick brown fox jumps over the lazy
dog";
string bar = Scramble(foo);
}

 

[Roger Frost]

Oh, and at some point will you need to restore the string to it's original
state?

 

[Mike P]

Roger,

Yes, exactly like that, but I won't need to restore the string to its
original state.


Thanks,

Mike

 

[Marc Gravell]

Sorry, should have been Next(i+1), otherwise it always starts with the
last character.

Actually, I'm amazed it didn't throw an exception, passing Next(0)
[although this is covered in the MSDN documentation, still...]

Marc

 

[Mike P]

Many thanks Marc!

 

[Arne Vajhøj]

Does anybody have a simple method for randomising the character
positions in a string?

using System;

namespace E
{
public class Program
{
private static Random rng = new Random();
public static void Main(string[] args)
{
string s = "Hello world !";
char[] c = s.ToCharArray();
byte[] b = new byte[c.Length];
rng.NextBytes(b);
Array.Sort<byte, char>(b, c);
string s2 = new string(c);
Console.WriteLine(s2);
Console.ReadKey();
}
}
}

It is not the most efficient method, but the code is simple.

Arne