Project Euler Problem 054

Statement

In the card game poker, a hand consists of five cards and are ranked, from lowest to highest, in the following way:

  • High Card: Highest value card.
  • One Pair: Two cards of the same value.
  • Two Pairs: Two different pairs.
  • Three of a Kind: Three cards of the same value.
  • Straight: All cards are consecutive values.
  • Flush: All cards of the same suit.
  • Full House: Three of a kind and a pair.
  • Four of a Kind: Four cards of the same value.
  • Straight Flush: All cards are consecutive values of same suit.
  • Royal Flush: Ten, Jack, Queen, King, Ace, in same suit.

The cards are valued in the order:
2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, King, Ace.

If two players have the same ranked hands then the rank made up of the highest value wins; for example, a pair of eights beats a pair of fives (see example 1 below). But if two ranks tie, for example, both players have a pair of queens, then highest cards in each hand are compared (see example 4 below); if the highest cards tie then the next highest cards are compared, and so on.

The file, poker.txt, contains one-thousand random hands dealt to two players. Each line of the file contains ten cards (separated by a single space): the first five are Player 1's cards and the last five are Player 2's cards. You can assume that all hands are valid (no invalid characters or repeated cards), each player's hand is in no specific order, and in each hand there is a clear winner.

How many hands does Player 1 win?

Solution

To solve this particular problem I use an object-oriented approach. Each type of poker hand is a subclass of the PokerHand class, then I use double dispatching to determine who the winner is.

class PokerHand:
 
    def __init__(self, cards):
        self.cards = cards
 
    @classmethod
    def create_hand(cls, cards):
        new_cards = []
        numbers = {}
        for n, c in cards:
            if n == 'T':
                n = 10
            elif n == 'J':
                n = 11
            elif n == 'Q':
                n = 12
            elif n == 'K':
                n = 13
            elif n == 'A':
                n = 14
            else:
                n = int(n)
            new_cards.append((n,c))
 
            numbers[n] = numbers.get(n, 0) + 1
 
        is_flush = len(set([c for n,c in new_cards])) == 1
        is_straight = len(numbers) == 5 and (max(numbers) - min(numbers) == 4 or set([2, 3, 4, 5, 14]) == set(numbers.keys()))
 
        if is_flush and is_straight:
            if set([2, 3, 4, 5, 14]) == set(numbers.keys()):
                numbers[1] = 1
                del numbers[14]
            return StraightFlush(numbers)
 
        if is_flush:
            return Flush(numbers)
 
        if is_straight:
            if set([2, 3, 4, 5, 14]) == set(numbers.keys()):
                numbers[1] = 1
                del numbers[14]
            return Straight(numbers)
 
        card_counts = sorted(numbers.values())
 
        if card_counts == [1,4]:
            return Poker(numbers)
 
        if card_counts == [2,3]:
            return FullHouse(numbers)
 
        if card_counts == [1,1,3]:
            return ThreeOfAKind(numbers)
 
        if card_counts == [1,2,2]:
            return DoublePair(numbers)
 
        if card_counts == [1,1,1,2]:
            return Pair(numbers)
 
        return HighCard(numbers)
 
class StraigthFlush(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsStraightFlush(self)
 
    def beatsStraightFlush(self, poker_hand):
        return max(self.cards) > max(poker_hand.cards)
 
    def beatsPoker(self, poker_hand):
        return True
 
    beatsFullHouse = beatsFlush = beatsStraight = beatsThreeOfAKind = beatsDoublePair = beatsPair = beatsHighCard = beatsPoker
 
class Poker(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsPoker(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    def beatsPoker(self, poker_hand):
        poker_card_me = next(filter(lambda k: self.cards[k] == 4, self.cards))
        poker_card_other = next(filter(lambda k: poker_hand.cards[k] == 4, poker_hand.cards))
        if poker_card_me > poker_card_other:
            return True
        else:
            return False
 
    def beatsFullHouse(self, poker_hand):
        return True
 
    beatsFlush = beatsStraight = beatsThreeOfAKind = beatsDoublePair = beatsPair = beatsHighCard = beatsFullHouse
 
class FullHouse(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsFullHouse(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsPoker = beatsStraightFlush
 
    def beatsFullHouse(self, poker_hand):
        full_card_me = next(filter(lambda k: self.cards[k] == 3, self.cards))
        full_card_other = next(filter(lambda k: poker_hand.cards[k] == 3, poker_hand.cards))
        return full_card_me > full_card_other
 
    def beatsFlush(self, poker_hand):
        return True
 
    beatsStraight = beatsThreeOfAKind = beatsDoublePair = beatsPair = beatsHighCard = beatsFlush
 
class Flush(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsFlush(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsFullHouse = beatsPoker = beatsStraightFlush
 
    def beatsFlush(self, poker_hand):
        my_cards = sorted(self.cards, key=lambda x: -x)
        other_cards = sorted(poker_hand.cards, key=lambda x: -x)
        return my_cards > other_cards
 
    def beatsStraight(self, poker_hand):
        return True
 
    beatsThreeOfAKind = beatsDoublePair = beatsPair = beatsHighCard = beatsStraight
 
class Straight(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsStraight(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsFlush = beatsFullHouse = beatsPoker = beatsStraightFlush
 
    def beatsStraight(self, poker_hand):
        return max(self.cards) > max(poker_hand.cards)
 
    def beatsThreeOfAKind(self, poker_hand):
        return True
 
    beatsDoublePair = beatsPair = beatsHighCard = beatsThreeOfAKind
 
class ThreeOfAKind(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsThreeOfAKind(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsStraight = beatsFlush = beatsFullHouse = beatsPoker = beatsStraightFlush
 
    def beatsThreeOfAKind(self, poker_hand):
        three_card_me = next(filter(lambda k: self.cards[k] == 3, self.cards))
        three_card_other = next(filter(lambda k: poker_hand.cards[k] == 3, poker_hand.cards))
        return three_card_me > three_card_other
 
    def beatsDoublePair(self, poker_hand):
        return True
 
    beatsPair = beatsHighCard = beatsDoublePair
 
class DoublePair(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsDoublePair(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsThreeOfAKind = beatsStraight = beatsFlush = beatsFullHouse = beatsPoker = beatsStraightFlush
 
    def beatsDoublePair(self, poker_hand):
        two_cards_me = sorted(filter(lambda k: self.cards[k] == 2, self.cards), key=lambda x: -x)
        two_cards_other = sorted(filter(lambda k: poker_hand.cards[k] == 2, poker_hand.cards), key=lambda x: -x)
        if two_cards_me > two_cards_other:
            return True
        elif two_cards_me < two_cards_other:
            return False
        else:
            one_card_me = next(filter(lambda k: self.cards[k] == 1, self.cards))
            one_card_other = next(filter(lambda k: poker_hand.cards[k] == 1, poker_hand.cards))
            return one_card_me > one_card_other
 
    def beatsPair(self, poker_hand):
        return True
 
    beatsHighCard = beatsPair
 
class Pair(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsPair(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsDoublePair = beatsThreeOfAKind = beatsStraight = beatsFlush = beatsFullHouse = beatsPoker = beatsStraightFlush
 
    def beatsPair(self, poker_hand):
        two_card_me = next(filter(lambda k: self.cards[k] == 2, self.cards))
        two_card_other = next(filter(lambda k: poker_hand.cards[k] == 2, poker_hand.cards))
        if two_card_me > two_card_other:
            return True
        elif two_card_me < two_card_other:
            return False
        else:
            one_cards_me = sorted(filter(lambda k: self.cards[k] == 1, self.cards), key=lambda x: -x)
            one_cards_other = sorted(filter(lambda k: poker_hand.cards[k] == 1, poker_hand.cards), key=lambda x: -x)
            return one_cards_me > one_cards_other
 
    def beatsHighCard(self, poker_hand):
        return True
 
class HighCard(PokerHand):
 
    def beats(self, poker_hand):
        return not poker_hand.beatsHighCard(self)
 
    def beatsStraightFlush(self, poker_hand):
        return False
 
    beatsPair = beatsDoublePair = beatsThreeOfAKind = beatsStraight = beatsFlush = beatsFullHouse = beatsPoker = beatsStraightFlush
 
    def beatsHighCard(self, poker_hand):
        return sorted(self.cards, key=lambda x: -x) > sorted(poker_hand.cards, key=lambda x: -x)
 
if __name__ == '__main__':
    result = sum(1 for line in open('poker.txt') if
                 PokerHand.create_hand(line.strip().split(' ')[:5]).beats(PokerHand.create_hand(line.strip().split(' ')[5:])))
    print("The result is:", result)

The Python file is available for download here.

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