概要

ポーカーの役判定アルゴリズムを示す。

判定コード

enum {
    HIGH_CARD = 0,
    ONE_PAIR,
    TWO_PAIR,
    THREE_OF_A_KIND,
    STRAIGHT,
    FLUSH,
    FULL_HOUSE,
    FOUR_OF_A_KIND,
    STRAIGHT_FLUSH,
    N_KIND_HAND,
};
// v のサイズは 7以下とする
// 要素はソートされていないものとする
int checkHand(const std::vector<Card> &v)
{
    std::vector<int> rcnt(13, 0);
    std::vector<int> scnt(4, 0);
    //int rcnt[13] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    //int scnt[4] = {0, 0, 0, 0};
    for (uint i = 0; i < v.size(); ++i) {
        const Card c = v[i];
        rcnt[c.m_rank] += 1;
        scnt[c.m_suit] += 1;
    }
    int s = -1;
    if( scnt[s = 0] >= 5 || scnt[s = 1] >= 5 || scnt[s = 2] >= 5 || scnt[s = 3] >= 5 ) {
        // フラッシュ確定
        uint bitmap = 0;
        for (uint i = 0; i < v.size(); ++i) {
            const Card c = v[i];
            if( c.m_suit == s )
                bitmap |= 1 << (c.m_rank);
        }
        uint mask = 0x1f00;       // AKQJT
        for (int i = 0; i < 9; ++i, mask>>=1) {
            if( (bitmap & mask) == mask ) {
                return STRAIGHT_FLUSH;
            }
        }
        if( bitmap == 0x100f )// 1 0000 00000 1111 = A5432
            return STRAIGHT_FLUSH;
    } else
        s = -1;
    int threeOfAKindIX = -1;
    int pairIX1 = -1;
    int pairIX2 = -1;
    for (int i = 0; i < 13; ++i) {
        switch( rcnt[i] ) {
            case 4:
                return FOUR_OF_A_KIND;
            case 3:
                threeOfAKindIX = i;
                break;
            case 2:
                pairIX2 = pairIX1;
                pairIX1 = i;
                break;
        }
    }
    if( threeOfAKindIX >= 0 && pairIX1 >= 0 )
        return FULL_HOUSE;
    if( s >= 0 )
        return FLUSH;
    uint bitmap = 0;
    uint mask = 1;
    for (int i = 0; i < 13; ++i, mask<<=1) {
        if( rcnt[i] != 0 )
            bitmap |= mask;
    }
    mask = 0x1f00;     // AKQJT
    for (int i = 0; i < 9; ++i, mask>>=1) {
        if( (bitmap & mask) == mask )
            return STRAIGHT;
    }
    if( bitmap == 0x100f )// 1 0000 00000 1111 = A5432
        return STRAIGHT;
    if( threeOfAKindIX >= 0 )
        return THREE_OF_A_KIND;
    if( pairIX2 >= 0 )
        return TWO_PAIR;
    if( pairIX1 >= 0 )
        return ONE_PAIR;
    return HIGH_CARD;
}