algorithm to sum up a list of numbers for all combinations

Question

I have a list of numbers and I want to add up all the different combinations. For example:

• number as 1,4,7 and 13
• the output would be:

Answer 1

This is not the code to generate the sums, but it generates the permutations. In your case:

1; 1,4; 1,7; 4,7; 1,4,7; ...

If I have a moment over the weekend, and if it's interesting, I can modify this to come up with the sums.

It's just a fun chunk of LINQ code from Igor Ostrovsky's blog titled "7 tricks to simplify your programs with LINQ" (http://igoro.com/archive/7-tricks-to-simplify-your-programs-with-linq/).

T[] arr = …;
var subsets = from m in Enumerable.Range(0, 1 << arr.Length)
              select
                  from i in Enumerable.Range(0, arr.Length)
                  where (m & (1 << i)) != 0
                  select arr[i];