Re: calculating cribbage points

[ikegami]

Pairs:

my %count;
++$count{$_} foreach @c;

my @pairs = grep { $count{$_} >= 2 } sort { $b <=> $a } @c;
my @kind3 = grep { $count{$_} >= 3 } @pairs;
my @kind4 = grep { $count{$_} >= 4 } @kind3;

Longest run:

@c = sort { $b <=> $a } @c;

my $lr_len = 0;
my $lr_idx;

my $s = 0;
while ($s <= 4) {
   my $e = $s+1;
   ++$e while $e <= 4 && $c[$e] == $c[$e-1] - 1;
   if ($e-$s > $lr_len) {
      $lr_len = $e-$s;
      $lr_idx = $s;
   }
   $s = $e;
}

All runs:

@c = sort { $b <=> $a } @c;

my @runs;

my $s = 0;
while ($s <= 4) {
   my $e = $s+1;
   ++$e while $e <= 4 && $c[$e] == $c[$e-1] - 1;
   if ($e-$s > 1) {
      push(@runs, [ map { $c[$_] } $s..$e-1 ]);
      $lr_idx = $s;
   }
   $s = $e;
}

# Sort by length, then by highest.
@runs = sort { @$b <=> @$a || $b->[0] <=> $a->[0] } @runs;

[Limbic~Region]

ikegami,
Your code:

my %count;
++$count{$_} foreach @c;

my @pairs = grep { $count{$_} >= 2 } sort { $b <=> $a } @c;
my @kind3 = grep { $count{$_} >= 3 } @pairs;
my @kind4 = grep { $count{$_} >= 4 } @kind3;

Can be simplified to:

my ($points, %count);
++$count{$_} for @c;
$points += $_ * ($_ - 1) for values %count;

I used this trick and several others in RFC: Cribbage::Hand.

[ikegami]

I don't know cribbage. I didn't even know we were dealing with cribbage. I didn't count the points, just list the pairs. Your code is not so much a simplification as something different.

[dracos]

I'm sorry could some one explain what is up with the code for runs. I can't get it to work and I am having troubles figuring out how it is suspose to work.

[ikegami]

You can't get them to run? Wierd, I've tested them. You shouldn't have any problems.

$s is the index of the card at the start of a run.
$e is the index of the card one beyond the end of a run.
"lr" stands for "longest run".
$lr_idx is the index of the card which starts the longest run.
$c[$lr_idx] is the face value of the card which starts the longest run.
$lr_len is the length of the run, as a number of cards.
@runs is an array of runs, where a run is a reference to an array of card face values.

[thor]

The thing about scoring mutiples (pairs, 3-of-a-kind, 4-of-a-kind) in cribbage is that it all just breaks down to scoring pairs. 3-of-a-kind is worth 6 points because there are 3-choose-2 pairs (which is 3) in a 3-of-a-kind. Each pair being worth 2 points yields 6 points total. So, using similar techniques as stated already in this thread, one can generate the set of all pairs and if the two elements in the pair are the same, increment the count of pairs.