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Re: Sum of N elements in an M element array

by Corion (Patriarch)
on Feb 01, 2020 at 09:11 UTC ( [id://11112220]=note: print w/replies, xml ) Need Help??


in reply to Sum of N elements in an M element array

There are many simple ways to do this. I would look at Data::PowerSet to generate sets of all numbers to sum, or program it myself by using the binary digits of a counter to indicate whether an element should be included:

00000 # (no element summed)
00001 #         e
00010 #       d
00011 #       d+e
00100 #     c
...
11111 # a+b+c+d+e

[download]

What code have you written and where do you have problems?

Replies are listed 'Best First'.
Re^2: Sum of N elements in an M element array
by abhay180 (Sexton) on Feb 02, 2020 at 07:56 UTC
    Thanks Corion. The exact problem is about finding all the combinations. I find Math:Combinatorics useful as well. Here is what i did to gather all 2-item combinations from N item array. I wasn't sure how i would do it for any M items. 
    @a=(1..5);
my @comb="";
for(my $i=0;$i<=$#a;$i++) {
  for(my $j=0;$j<=$#a;$j++) {
      next if $i==$j;
      if ($a[$i] < $a[$j]) { push @comb, "$a[$i] , $a[$j]" ; }
      else                 { push @comb, "$a[$j] , $a[$i]" ; }
}
}
shift @comb;
use List::MoreUtils qw(uniq);
@comb = uniq(@comb);

    [download]
[reply]
[d/l]
      Thanks all for your suggestions. I managed w Math:Combinatorics to get what i want.
[reply]

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