Task: Poker hand analyser





Java: import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;

public class PokerHandAnalyzer {

    final static String faces = "AKQJT98765432";
    final static String suits = "HDSC";
    final static String[] deck = buildDeck();

    public static void main(String[] args) {
        System.out.println("Regular hands:\n");
        for (String input : new String[]{"2H 2D 2S KS QD",
            "2H 5H 7D 8S 9D",
            "AH 2D 3S 4S 5S",
            "2H 3H 2D 3S 3D",
            "2H 7H 2D 3S 3D",
            "2H 7H 7D 7S 7C",
            "TH JH QH KH AH",
            "4H 4C KC 5D TC",
            "QC TC 7C 6C 4C",
            "QC TC 7C 7C TD"}) {
            System.out.println(analyzeHand(input.split(" ")));
        }

        System.out.println("\nHands with wildcards:\n");
        for (String input : new String[]{"2H 2D 2S KS WW",
            "2H 5H 7D 8S WW",
            "AH 2D 3S 4S WW",
            "2H 3H 2D 3S WW",
            "2H 7H 2D 3S WW",
            "2H 7H 7D WW WW",
            "TH JH QH WW WW",
            "4H 4C KC WW WW",
            "QC TC 7C WW WW",
            "QC TC 7H WW WW"}) {
            System.out.println(analyzeHandWithWildcards(input.split(" ")));
        }
    }

    private static Score analyzeHand(final String[] hand) {
        if (hand.length != 5)
            return new Score("invalid hand: wrong number of cards", -1, hand);

        if (new HashSet<>(Arrays.asList(hand)).size() != hand.length)
            return new Score("invalid hand: duplicates", -1, hand);

        int[] faceCount = new int[faces.length()];
        long straight = 0, flush = 0;
        for (String card : hand) {

            int face = faces.indexOf(card.charAt(0));
            if (face == -1)
                return new Score("invalid hand: non existing face", -1, hand);
            straight |= (1 << face);

            faceCount[face]++;

            if (suits.indexOf(card.charAt(1)) == -1)
                return new Score("invalid hand: non-existing suit", -1, hand);
            flush |= (1 << card.charAt(1));
        }

        
        while (straight % 2 == 0)
            straight >>= 1;

        
        boolean hasStraight = straight == 0b11111 || straight == 0b1111000000001;

        
        boolean hasFlush = (flush & (flush - 1)) == 0;

        if (hasStraight && hasFlush)
            return new Score("straight-flush", 9, hand);

        int total = 0;
        for (int count : faceCount) {
            if (count == 4)
                return new Score("four-of-a-kind", 8, hand);
            if (count == 3)
                total += 3;
            else if (count == 2)
                total += 2;
        }

        if (total == 5)
            return new Score("full-house", 7, hand);

        if (hasFlush)
            return new Score("flush", 6, hand);

        if (hasStraight)
            return new Score("straight", 5, hand);

        if (total == 3)
            return new Score("three-of-a-kind", 4, hand);

        if (total == 4)
            return new Score("two-pair", 3, hand);

        if (total == 2)
            return new Score("one-pair", 2, hand);

        return new Score("high-card", 1, hand);
    }

    private static WildScore analyzeHandWithWildcards(String[] hand) {
        if (Collections.frequency(Arrays.asList(hand), "WW") > 2)
            throw new IllegalArgumentException("too many wildcards");

        return new WildScore(analyzeHandWithWildcardsR(hand, null), hand.clone());
    }

    private static Score analyzeHandWithWildcardsR(String[] hand,
            Score best) {

        for (int i = 0; i < hand.length; i++) {
            if (hand[i].equals("WW")) {
                for (String card : deck) {
                    if (!Arrays.asList(hand).contains(card)) {
                        hand[i] = card;
                        best = analyzeHandWithWildcardsR(hand, best);
                    }
                }
                hand[i] = "WW";
                break;
            }
        }
        Score result = analyzeHand(hand);
        if (best == null || result.weight > best.weight)
            best = result;
        return best;
    }

    private static String[] buildDeck() {
        String[] dck = new String[suits.length() * faces.length()];
        int i = 0;
        for (char s : suits.toCharArray()) {
            for (char f : faces.toCharArray()) {
                dck[i] = "" + f + s;
                i++;
            }
        }
        return dck;
    }

    private static class Score {
        final int weight;
        final String name;
        final String[] hand;

        Score(String n, int w, String[] h) {
            weight = w;
            name = n;
            hand = h != null ? h.clone() : h;
        }

        @Override
        public String toString() {
            return Arrays.toString(hand) + " " + name;
        }
    }

    private static class WildScore {
        final String[] wild;
        final Score score;

        WildScore(Score s, String[] w) {
            score = s;
            wild = w;
        }

        @Override
        public String toString() {
            return String.format("%s%n%s%n", Arrays.toString(wild),
                    score.toString());
        }
    }
}