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List all the possible combinations of three numbers from a given sample.

Posted on 2013-02-04
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Last Modified: 2013-03-20
I have to work out and write down all the possible combinations of three numbers can be extracted (without repetition) from 80.

as an illustration:

there is only one group of three numbers in 3 (1,2,3)
there are four groups of three numbers in 4 (1,2,3  1,2,4  1,3,4  2,3,4)
there are 10 groups of three numbers in 6

I have for the calculation =COMBIN(80, 3) for excel which gives me 18,424 possibilities, so I know how many combinations are possible

I need code that will list all them written out in a spreadsheet in an list probably in a text document

I would be very grateful for help
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Question by:MichaelGlancy
9 Comments
 
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Expert Comment

by:TommySzalapski
ID: 38852456
This is a duplicate of http:Q_28019535.html
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Expert Comment

by:wilcoxon
ID: 38852610
Simple to do...

my @arr = #list of 80 numbers - either entered directly in code or read from file
open OUT, ">output.csv" or die "could not write output: $!";
for my $i (0..79) {
    for my $j (($i+1)..79) {
        for my $k (($j+1)..79) {
            print OUT "$i,$j,$k\n";
        }
    }
}
close OUT;

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Author Comment

by:MichaelGlancy
ID: 38853082
TommySzalapski

it is a duplicate because I was advised to try Perl, so I reposted from excel to Perl
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Expert Comment

by:tel2
ID: 38853119
Hi Michael,

wilcoxon's code looks good to me, except:
- I don't see the point of line 1, since @arr is not referenced elsewhere.
- From your examples, it looks as if you want numbers to be 1 to 80, not 0 to 79.

Here's the code with those minor adjustments:
#!/usr/bin/perl

open OUT, ">output.csv" or die "Could not write output: $!";
for my $i (1..80) {
    for my $j (($i+1)..80) {
        for my $k (($j+1)..80) {
            print OUT "$i,$j,$k\n";
        }
    }
}
close OUT;

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Both scripts produce 82,160 rows of output, which is what =COMBIN(80, 3) gives me when I run it in Excel 2003.
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Expert Comment

by:wilcoxon
ID: 38853534
Good point - typo in my code.  It says "from 80 numbers" so I'm assuming it is not simply the numbers 1-80 (if it is simply 1-80 then tel2's changes to my code will work).

my @arr = #list of 80 numbers - either entered directly in code or read from file
open OUT, ">output.csv" or die "could not write output: $!";
for my $i (0..79) {
    for my $j (($i+1)..79) {
        for my $k (($j+1)..79) {
            print OUT "$arr[$i],$arr[$j],$arr[$k]\n";
        }
    }
}
close OUT;

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Expert Comment

by:TommySzalapski
ID: 38855081
it is a duplicate because I was advised to try Perl, so I reposted from excel to Perl
What you could do next time is just hit the 'Request Attention' button and ask the Admins to add the Perl zone to the old question. That will generate emails to all the Perl experts asking them to check out your question.

I still don't see why you need something other than Excel for this though for 82k possibilities. Try doing it with the VBA code I posted (it's very similar to the Perl code here). It should work.
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Accepted Solution

by:
FishMonger earned 500 total points
ID: 38856458
There are a number of modules on cpan that does this for you very easily.

Unless I'm misunderstanding what you want, I think you'll end up with more combinations than what you think.

Here's my test script.
#!/usr/bin/perl

use strict;
use warnings;
use Math::Combinatorics;

my @set = 1..6;
my $combinat = Math::Combinatorics->new(count => 3, data => [@set]);

my $cnt;
while(my @permu = $combinat->next_combination){
    print join(' ', @permu)."\n";
    $cnt++;
}

print "\n$cnt\n";

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Output of:
c:\testing>permutations.pl
6 5 4
6 5 3
6 5 2
6 5 1
6 4 3
6 4 2
6 4 1
6 3 2
6 3 1
6 2 1
5 4 3
5 4 2
5 4 1
5 3 2
5 3 1
5 2 1
4 3 2
4 3 1
4 2 1
3 2 1

20
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LVL 31

Expert Comment

by:GwynforWeb
ID: 38871655
In Java or C++ like syntax it is, (this is JavaScript)

<script>

n=5
for (i=1;i<=n;i++)
 for (j=i+1;j<=n;j++)
   for (k=j+1;k<=n;k++)
     document.write(i +' '+ j+ ' '+ k +"<br>")

</script>

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You can run this by copying and pasting into Notepad, saving as a .htm and opening in a browser.

Test n=5
1 2 3
1 2 4
1 2 5
1 3 4
1 3 5
1 4 5
2 3 4
2 3 5
2 4 5
3 4 5
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Expert Comment

by:Danean
ID: 39005096
I like the Java version where you can open the list in a browser.  Is there also a way to send the output list to a txt file with the java script?
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