How to get "One -one" permutation string from a List<String> in C# using LINQ

Question

I'm having a list of string

List<String> MyList=new List<String>{ "A,B" , "C,D,E" , "F,G" };

I need to convert the List "MyList" into the following format

"A-B"
"B-A"
"C-D"
"C-E"
"D-C"
"D-E"
"E-C"
"E-D"
"F-G"
"G-F"

Now i'm using something like spliting each item by "," and then adding that to a new list, then taking combination and then performing union operation among all the lists.

Is there any way to do this using LINQ?

Just a warning - you can expect this to get fairly expensive wrt. time as soon as you've more than a large handful (!) of elements in one of your strings. — Will A
– Will A, Commented Sep 21, 2010 at 5:49
not sure if you already have an iterative solution and you're just trying to find a more 'elegant' perspective, but here's a look at performance of one vs the other: stackoverflow.com/questions/1044236/… — Oren Mazor
– Oren Mazor, Commented Sep 21, 2010 at 5:51
By the way, you must tell others what do you want if there is A,B,A in the list. — Cheng Chen
– Cheng Chen, Commented Sep 21, 2010 at 6:04

mancaus · Accepted Answer · 2010-09-21 06:55:10Z

3

Something like this, assuming no repeats in each list.

from a in new List<String>{ "A,B" , "C,D,E" , "F,G" }
select a.Split(',') into b
from c in b
from d in b
where c != d
select c + "-" + d

A bit more awkward to allow duplicates:

(new List<String>{ "A,B" , "C,D,E" , "F,G" }).Select(csv => 
    csv.Split(',')
    .SelectMany((a,i) => csv.Split(',').Select((b,j) => new { a, i, b, j } ))
    .Where(r => r.i != r.j)
    .Select(r => r.a + "-" + r.b))

edited Sep 21, 2010 at 6:55

answered Sep 21, 2010 at 5:51

mancaus

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1 Comment

John Buchanan Over a year ago

Nice answer. But you forgot the "-" in the op's question.

Bennor McCarthy · Accepted Answer · 2010-09-21 05:55:24Z

2

var items = new List<string>{ "A,B" , "C,D,E" , "F,G" };
var results = from x in items
              let y = x.Split(',')
              from z1 in y
              from z2 in y
              where z1 != z2
              select string.Format("{0}-{1}", z1, z2);

answered Sep 21, 2010 at 5:55

Bennor McCarthy

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1 Comment

Timwi Over a year ago

This assumes that the strings between commas are unique. If the input list contains only "A,A" this will not output anything, but I would expect "A-A".

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