C# How to permutate all elements with each others in a List of string

Question

I have a string list and i want all permutations of all elements with each others

Example :

var myList = new List<string>{ "AB", "CD", "EF", "GK" };

and as result i want a string like this.

var resultStr = "ABCD,ABEF,ABGK,CDAB,CDEF,CDGK,EFAB,EFCD,EFGK,GKAB,GKCD,GKEF";

note that resultStr doesnt include "ABAB","CDCD","EFEF","GKGK"

is there any short way to do this except double for/foreach loops?

Answer 1

Q: is there any short way to do this except double for/foreach loops?

Yes, you can use LINQ.

Here's the LINQ syntax expression for your result:

var myList = new List<string>{ "AB", "CD", "EF", "GK" };
var result = from a in myList from b in myList where a != b select a+b;
var resultStr = string.Join(",", result);
Console.WriteLine(resultStr);

You can also use the LINQ extension methods:

var myList = new List<string>{ "AB", "CD", "EF", "GK" };
var result = myList.SelectMany(a => myList.Where(b => b != a).Select(b => a + b));
var resultStr = string.Join(",", result);
Console.WriteLine(resultStr);

Both will output

ABCD,ABEF,ABGK,CDAB,CDEF,CDGK,EFAB,EFCD,EFGK,GKAB,GKCD,GKEF

.NET Fiddle so you can try it