7 Replies Latest reply: Sep 2, 2010 8:42 AM by 843853

Combinations Algorithm

I have a few Lists of Strings. for example:

List<String> AList contains {"a1","a2","a3","a4"}
List<String> BList contains {"b1","b2","b3"}
List<String> CList contains {"c1","c2","c3","c4","c5"}
List<String> DList contains {"d1","d2"}

so on and so forth. The number of lists is variable and number of Strings in the list is also variable. I want to write a code that returns ALL POSSIBLE combinations under the following conditions:

1) each set contains at least two elements. In this example the each set will contain 2 to 5 elements. - example: {"a1","b1"} or {"c2","b3","d2"}
2) each element in a set is from different lists - example: {"c1","c4"} or {"b1","b2","a4"} both are invalid.
3) each set has unique combination of elements - example: {"a3", "d2", "b4"} is equivalent to {"d2", "a3", "b4"} hence if {"a3", "d2", "b4"} is returned in the results {"d2", "a3", "b4"} should not be returned.

I am using Java.
• 1. Re: Combinations Algorithm
Okay, and what's your question? We can't really answer general "how do I do this" type questions other than by pointing you to the basic tutorials.

Post some code, in SSCCE form, demonstrating where you got stuck. Ask a specific question.

PS- Am I reading it right that you registered 10 years ago, but only made your first post now?
• 2. Re: Combinations Algorithm
Cross posted - [http://www.coderanch.com/t/508944/java/java/Combinations-Algorithm|http://www.coderanch.com/t/508944/java/java/Combinations-Algorithm].
• 3. Re: Combinations Algorithm
Can I see those basic tutorials?

You are correct about the PS. Thanks to hardworking people like you I never had to ask an original questions before.
• 4. Re: Combinations Algorithm
Can I see those basic tutorials?
Sure. A quick google of "java tutorial" came up with this, which is full of great information.
You are correct about the PS. Thanks to hardworking people like you I never had to ask an original questions before.
Interesting. Surely in that time you've also seen how people respond to general "how do I do this" type questions and especially cross-posting?
• 5. Re: Combinations Algorithm
kevinaworkman If you do not want to help can you please stay off this? This is nonsense.