c# - Getting all the combinations in an array

Question

Say I have the following array:

var arr = new[] { "A", "B", "C" };

How can I produce all the possible combinations that contain only two characters and no two the same (e.g. AB would be the same as BA). For example, using the above array it would produce:

AB
AC
BC

Please note that this example has been simplified. The array and the length of the string required will be greater.

I'd really appreciate if someone could help.

Answer 1

Lets extend it, so maybe we can see the pattern:

string[] arr = new string[] { "A", "B", "C", "D", "E" };

//arr[0] + arr[1] = AB
//arr[0] + arr[2] = AC
//arr[0] + arr[3] = AD
//arr[0] + arr[4] = AE

//arr[1] + arr[2] = BC
//arr[1] + arr[3] = BD
//arr[1] + arr[4] = BE

//arr[2] + arr[3] = CD
//arr[2] + arr[4] = CE

//arr[3] + arr[4] = DE

I see two loops here.

• The first (outer) loop goes from 0 to 4 (arr.Length - 1)
• The second (inner) loop goes from the outer loops counter + 1 to 4 (arr.Length)

Now it should be easy to translate that to code!