Every 2 Letter Combo for Array of Strings

[sloan]

string[] array = new string[3] {"A","B","C"};
Given the above data, I'm trying to find C# code which will produce


A,A
B,A
C,A
A,B
B,B
C,B
A,C
B,C
C,C
Its been a long week, and I'm brain dead, and googled out.
Thanks for any help.

[Marc Gravell]

Erm, loop?

string[] array = { "A", "B", "C" };
for(int i = 0; i < array.Length; i++)
for (int j = 0; j < array.Length; j++)
{
Console.WriteLine("{0},{1}", array[j], array[i]);
}

You could do something more exciting, but that should do...

Marc

[sloan]

Like I said dude....brain dead.
"Marc Gravell" <ma**********@gmail.comwrote in message
news:79**********************************@v4g2000h sf.googlegroups.com...

Erm, loop?

string[] array = { "A", "B", "C" };
for(int i = 0; i < array.Length; i++)
for (int j = 0; j < array.Length; j++)
{
Console.WriteLine("{0},{1}", array[j], array[i]);
}

You could do something more exciting, but that should do...

Marc

[Nicholas Paldino [.NET/C# MVP]]

Something more exciting being (if the OP is using .NET 3.5/C# 3.0):

string[] array = { "A", "B", "C" };

IEnumerable<stringquery =
from a in array
from b in array
select a + "," + b // Could be string.Format("{0},{1}", a, b) as well if
you wish.

foreach (string item in query)
{
Console.WriteLine(item);
}

--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com
"Marc Gravell" <ma**********@gmail.comwrote in message
news:79**********************************@v4g2000h sf.googlegroups.com...

Erm, loop?

string[] array = { "A", "B", "C" };
for(int i = 0; i < array.Length; i++)
for (int j = 0; j < array.Length; j++)
{
Console.WriteLine("{0},{1}", array[j], array[i]);
}

You could do something more exciting, but that should do...

Marc

[Marc Gravell]

Like I said dude....brain dead.

I know that feeling;-p

Currently in "crunch"; I don't expect to be getting to sleep any time
soon...

Marc

[Marc Gravell]

(laughs)

I actually deliberately stopped myself posting the LINQ version, aware
(over-cautious) that LINQ isn't yet fully mainstream... oh well ;-p

Marc

[Marc Gravell]

IEnumerable<stringquery =

* * ...
* * select new { A1Label = a, A2Label = b, NotSame = (a != b) };

(minor; just for the OP really) - you'd need "var query" here because
of the anonymous type in the projection

Marc

[Jeroen Mostert]

Nicholas Paldino [.NET/C# MVP] wrote:

Well, in SQL, you don't have to explicitly state CROSS JOIN anymore (and
I do believe it is actually not recommended now, but I'd have to look that
up), you can just do:

select
a1.AlphabetLabel as A1Label, a2.AlphabetLabel as A2Label,
case a1.AlphabetLabel when a2.AlphabetLabel then 0 else 1 end as NotSame
from
Alphabet as a1, Alphabet as a2

CROSS JOIN was introduced in SQL-92 to solve some ambiguity problems with
the comma notation and increase clarity (before this you couldn't use them,
so it's not a case of "not having to state it anymore"; the comma notation
came first). I'm not aware of any explicit recommendation for or against,
and either syntax will work fine.

However, it's still a very good idea to write out the CROSS JOIN explicitly,
since it's the most uncommon form of join (even if it's the most natural
one, mathematically speaking) and alerting your fellow developer to its use
is a good idea. An "accidental" cross join is not a good thing to have (as
even moderately-sized tables will produce enormous result sets) which is
exactly why ANSI SQL introduced explicit syntax for them.

--
J.

[Marc Gravell]

that'd better not be a ghost-busters joke!