Re: Algorithm problem: Order matches by difference between players

To solve this problem assign the first seed to play last seeded player in the first round and against a higher seed each subsequent round.

Then simply rely on the round-robin algorithm of rotating an array's values while keeping one static to ensure that everyone plays against each other:

use strict;
use warnings;

my $num_players = 6;

my @players = (1..$num_players);
push @players, 'bye' if @players % 2; # Even number

my $num_rounds = @players - 1;

for my $round (1..$num_rounds) {
    # Fold array to assign matches
    my @matches = map {join('-', sort @players[$_, $#players - $_])} (
+0..@players/2-1);

    # Print Results
    print "$round) " . join(', ', @matches), "\n";
    
    # Rotate last position to second
    splice @players, 1, 0, pop(@players);
}
[download]

Results:

1) 1-6, 2-5, 3-4
2) 1-5, 4-6, 2-3
3) 1-4, 3-5, 2-6
4) 1-3, 2-4, 5-6
5) 1-2, 3-6, 4-5
[download]

This works with any number of players and rounds.

Comment on Re: Algorithm problem: Order matches by difference between players Select or Download Code

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Re^2: Algorithm problem: Order matches by difference between players by Dirk80 (Pilgrim) on Apr 18, 2011 at 20:32 UTC
Usually I just vote positive. But this time I had to write a little post to say thank you for so many good answers in a very short time. I'm really impressed. I'm writing a lot of code which is not working for all cases. And you just write some lines of code and it is really working for every case.	[reply]
Re^3: Algorithm problem: Order matches by difference between players by wind (Priest) on Apr 18, 2011 at 20:53 UTC
One of my first jobs during the dotcom boom was a gaming website that ran tournaments and analyzed statistics. Coming up with algorithms for round robin, single, and double elimination tournaments was one of the first things I did. A more fun problem is to come up with an algorithm to page a double or single elimination tournament with a large number of seeds. You can of course just do it by hand, but it's more fun if you can configure how many rounds and pairings to show on each page. Glad we could help. - Miller	[reply]
Re^3: Algorithm problem: Order matches by difference between players by Ghalko (Novice) on Apr 18, 2011 at 21:29 UTC
The reason I can think of why you were having specific problems with 6 is because it isn't a power of two. Having set up fencing brackets for tournaments this is definitely true for single elimination, but it might also be true for a round robin if you are essentially running it as a no elimination bracket. I bet you would have problems with 10, 12, 14, evens that aren't a power of two, and all n-1 of those numbers with your code. Just an idea really, sort of fun to think about, maybe extremely useful for any tournament above 8 or so.	[reply]
Which is the oldest post in the monastery? by LanX (Saint) on Apr 18, 2011 at 23:00 UTC
~~Wow, Dirk80 you just wrote the 800000th post of the monastery!~~ Hmm I really thought id 100001 was the beginning since id 100000 is (kind of) a user profile. UPDATE: search form for some really old posts ?node_id=3989;nf=0;Wi;D;M, just hit search button! Cheers Rolf	[reply]