Perl, 414 398 370/458 344/416 char
Line breaks are not significant.
%M=map{$_,$Z++}0..9,T,J,Q,K,A;sub N{/.$/;$M{$`}.$&}
sub B{$s=@p=();
for$m(@_){$m-$_||($s+=2,++$p[$m])for@_}
@_=sort{$p[$b]-$p[$a]||$b-$a}@_;
$s=23 if$s<11&&($_[0]-$_[4]<5||$_[0]-$_[1]>8&&push@_,shift);
"@_"=~/.$/;$s+=14*(4<grep/$&/,@_);
$s=100*$s+$_ for@_;$s}
++$X{B((@c=map{N}split)[0..4])<=>B(@c[5..9])}for<>;
printf"1: %d\n2: %d\nD: %d\n",@X{1,-1,0}
This solves the "10 card" problem (10 cards are dealt, player 1 has the first 5 cards and player 2 has the second 5 cards).
The first section defines a subroutine N that can transform each card so that it has a numerical value. For non-face cards, this is a trivial mapping (5H ==> 5H) but it does transform the face cards (KC => 13C, AD => 14D).
The last section parses each line of input into cards, transforms the cards to contain numerical values, divides the cards into separate hands for the two players, and analyzes and compares those hands. Every hand increments one element of the hash %X. When all the input is parsed, %X contains the number of hands won by player 1, won by player 2, or ties.
The middle section is a subroutine that takes a set of five cards as input and produces a
12-digit number with the property that stronger poker hands will have higher-valued numbers. Here's how it works:
for$m(@_){$m-$_||($s+=2,++$p[$m])for@_}
This is the "pair" detector. If any two cards have the same numerical value, increment a hash element for one of the cards and increase the "score" variable $s by two. Note that we will end up comparing each card to itself, so $s will be at least 10 and $p[$x] will be at least one for every card $x. If the hand contains three of a kind, then those three cards will match with the other two cards -- it will be like there are 9 matches among those three cards and the "score" will be at least 18.
@_=sort{$p[$b]-$p[$a]||$b-$a}@_;
Sort the cards by (1) the number of times that card is part of a "pair" and (2) the value of the card. Thus in a hand with two 7's and two 3's, the two 7's will appear first, followed by the two 3's, followed by the kicker. In a hand with two 7's and three 3's, the three 3's will be first followed by the two 7's. The goal of this ordering is to distinguish two hands that have the same score -- a hand with a pair of 8's and a hand with a pair of 7's both have one pair, but we need to be able to tell that a pair of 8's is better.
$s=23 if$s<11&&($_[0]-$_[4]<5||$_[0]-$_[1]>8&&push@_,shift);
This line is the "straight" detector. A straight is worth 23 points and occurs when there are no pairs in the hand ($s<11 means only 5 "pairs" - each card matching with itself - were found) and either (1) the value of the highest card is exactly four more than the value of the lowest card ($_[0]-$_[4]==4), or (2) the highest value card is an Ace and the next highest card is a 5 ($_[0]-$_[1]==9), which means the hand has an A-2-3-4-5 straight. In the latter case, the Ace is now the least valuable card in the hand, so we manipulate @_ to reflect that (push@_,shift)
"@_"=~/.$/;$s+=14*(4<grep/$&/,@_);
This line is the flush detector. A flush is worth 14 more points and occurs when the last character is the same for each card. The first expression ("@_"=~/.$/) has the side effect of setting $& to the last character (the suit) of the last card in the hand. The final expression (4<grep/$&/,@_) will be true if and only if all elements of @_ have the same last character.
$s=100*$s+$_ for@_;$s}
Creates and returns a value that begins with the hand's score and then contains the values of the cards, in order of the card's importance. Scores for the various hands will be
Hand Score
---------- ------
High card 10 (each card matches itself for two points)
One pair 14 (2 additional matches)
Two pair 18 (4 additional matches)
Three of a kind 22 (6 additional matches)
Straight 23 (no pair, but 23 points for straight)
Flush 24 (no pair, but 14 additional points for the flush)
Full house 26 (8 additional matches)
4 of a kind 34 (12 additional matches)
Straight flush 37 (23 + 14 points)
which is consistent with the rules of poker. Hands with the same score can be distinguished by the values of the hand's cards, in order of importance to the hand, all the way down to the least valuable card in the hand.
The solution to the 9 card problem (two cards to player 1, two cards to player 2, the players share the next 5 cards and build their best 5 card hand) needs about 70 more strokes to choose the best 5 card hand out of the 7 cards available to each player:
%M=map{$_,$Z++}0..9,T,J,Q,K,A;sub N{/./;$M{$&}.$'}
sub A{my$I;
for$k(0..41){@d=@_;splice@d,$_,1for$k%7,$k/7;$s=@p=();
for$m(grep$_=N,@d){$m-$_||($s+=2,$p[$m]++)for@d}
@d=sort{$p[$b]-$p[$a]||$b-$a}@d;
$s=23 if$s<11&&($d[0]-$d[4]<5||$d[0]-$d[1]>8&&push@d,shift@d);
"@d"=~/.$/;$s+=14*(4<grep/$&/,@d);
$s=100*$s+$_ for@d;
$I=$s if$s>$I}$I}
++$X{A((@c=split)[0,1,4..8])<=>A(@c[2..8])}for<>;
printf"1: %d\n2: %d\nD: %d\n",@X{1,-1,0}
[[5S 6S] [2D 4D] [9S AS KD JS 9D]]is not a draw. You successively weed out equal best hands (from a five card hand regardless of how many cards are available) until either one player does indeed have a better best hand or until all five cards are gone in wich there is a draw. So in this case player 1 wins, as a 6 is higher than a 4. (Their other highest cards are all in the community hand.) This is how I implemented my Haskell solution. Now if we had[[5S 6S] [2D 6D] [9S AS KD JS 9D]], then we would have a draw. The5Sand2Dhave no impact on the game. – Cording