poker.py

"""
Poker Ranker for Exercism.io
"""


def best_hands(hands):
    hands = serialize(hands)
    return [
        deserialize(hand)
        for hand in hands
        if card_ranks(hand) == card_ranks(max(hands, key=hand_rank))
    ]


def serialize(hands):
    """["10C AH"] -> [("0", "C"), ("A", "H"),]"""
    _hands = []
    for hand in hands:
        _hand = []
        for card in hand.split():
            _hand.append((card[-2], card[-1]))
        _hands.append(_hand)
    return _hands


def deserialize(hand):
    """[("0", "C"), ("A", "H"),] -> ["10C AH"]"""
    return " ".join(["".join(["10" if r == "0" else r, s]) for r, s in hand])


def hand_rank(hand):
    """takes serialized hands and resturns its ranking"""
    ranks = card_ranks(hand)
    groups = [(ranks.count(i), i) for i in set(ranks)]
    groups.sort(reverse=True)
    counts, number = zip(*groups)
    straight = (len(counts) == 5) and (max(number) - min(number) == 4)
    flush = len(set([s for r, s in hand])) == 1
    return (
        8 if straight and flush else
        7 if counts == (4, 1) else
        6 if counts == (3, 2) else
        5 if flush else
        4 if straight else
        3 if counts == (3, 1, 1) else
        2 if counts == (2, 2, 1) else
        1 if counts == (2, 1, 1, 1) else
        0, number
    )


def card_ranks(hand):
    ranks = ["--234567890JQKA".index(r) for r, s in hand]
    ranks.sort(reverse=True)
    return [5, 4, 3, 2, 1] if (ranks == [14, 5, 4, 3, 2]) else ranks


# ------------ TESTS ------------


def test_single_hand_always_wins():
    hands = ["4S 5S 7H 8D JC"]
    expected = ["4S 5S 7H 8D JC"]
    assert best_hands(hands) == expected


def test_highest_card_out_of_all_hands_wins():
    hands = [
        "4D 5S 6S 8D 3C",
        "2S 4C 7S 9H 10H",
        "3S 4S 5D 6H JH",
    ]
    expected = ["3S 4S 5D 6H JH"]
    assert best_hands(hands) == expected


def test_tie_has_multiple_winners():
    hands = [
        "4D 5S 6S 8D 3C",
        "2S 4C 7S 9H 10H",
        "3S 4S 5D 6H JH",
        "3H 4H 5C 6C JD",
    ]
    expected = [
        "3S 4S 5D 6H JH",
        "3H 4H 5C 6C JD",
    ]
    assert best_hands(hands) == expected


def test_tie_compares_multiple():
    hands = [
        "3S 5H 6S 8D 7H",
        "2S 5D 6D 8C 7S",
    ]
    expected = ["3S 5H 6S 8D 7H"]
    assert best_hands(hands) == expected


def test_one_pair_beats_high_card():
    hands = [
        "4S 5H 6C 8D KH",
        "2S 4H 6S 4D JH",
    ]
    expected = ["2S 4H 6S 4D JH"]
    assert best_hands(hands) == expected


def test_highest_pair_wins():
    hands = [
        "4S 2H 6S 2D JH",
        "2S 4H 6C 4D JD",
    ]
    expected = ["2S 4H 6C 4D JD"]
    assert best_hands(hands) == expected


def test_two_pairs_beats_one_pair():
    hands = [
        "2S 8H 6S 8D JH",
        "4S 5H 4C 8C 5C",
    ]
    expected = ["4S 5H 4C 8C 5C"]
    assert best_hands(hands) == expected


def test_two_double_pair():
    hands = [
        "2S 8H 2D 8D 3H",
        "4S 5H 4C 8S 5D",
    ]
    expected = ["2S 8H 2D 8D 3H"]
    assert best_hands(hands) == expected


def test_two_double_pair_higher_tie():
    hands = [
        "2S QS 2C QD JH",
        "JD QH JS 8D QC",
    ]
    expected = ["JD QH JS 8D QC"]
    assert best_hands(hands) == expected


def test_two_double_pair_tie_kicker():
    hands = [
        "JD QH JS 8D QC",
        "JS QS JC 2D QD",
    ]
    expected = ["JD QH JS 8D QC"]
    assert best_hands(hands) == expected


def test_three_of_a_kind_beats_two_pair():
    hands = [
        "2S 8H 2H 8D JH",
        "4S 5H 4C 8S 4H",
    ]
    expected = ["4S 5H 4C 8S 4H"]
    assert best_hands(hands) == expected


def test_two_triple_pair():
    hands = [
        "2S 2H 2C 8D JH",
        "4S AH AS 8C AD",
    ]
    expected = ["4S AH AS 8C AD"]
    assert best_hands(hands) == expected


def test_two_three_multiple_decks():
    hands = [
        "4S AH AS 7C AD",
        "4S AH AS 8C AD",
    ]
    expected = ["4S AH AS 8C AD"]
    assert best_hands(hands) == expected


def test_three_vs_straight():
    hands = [
        "4S 5H 4C 8D 4H",
        "3S 4D 2S 6D 5C",
    ]
    expected = ["3S 4D 2S 6D 5C"]
    assert best_hands(hands) == expected


def test_aces_can_end_straight():
    hands = [
        "4S 5H 4C 8D 4H",
        "10D JH QS KD AC",
    ]
    expected = ["10D JH QS KD AC"]
    assert best_hands(hands) == expected


def test_aces_can_start_straight():
    hands = [
        "4S 5H 4C 8D 4H",
        "4D AH 3S 2D 5C",
    ]
    expected = ["4D AH 3S 2D 5C"]
    assert best_hands(hands) == expected


def test_two_straights():
    hands = [
        "4S 6C 7S 8D 5H",
        "5S 7H 8S 9D 6H",
    ]
    expected = ["5S 7H 8S 9D 6H"]
    assert best_hands(hands) == expected


def test_lowest_straight():
    hands = [
        "2H 3C 4D 5D 6H",
        "4S AH 3S 2D 5H",
    ]
    expected = ["2H 3C 4D 5D 6H"]
    assert best_hands(hands) == expected


def test_straight_vs_flush():
    hands = [
        "4C 6H 7D 8D 5H",
        "2S 4S 5S 6S 7S",
    ]
    expected = ["2S 4S 5S 6S 7S"]
    assert best_hands(hands) == expected


def test_two_flushes():
    hands = [
        "4H 7H 8H 9H 6H",
        "2S 4S 5S 6S 7S",
    ]
    expected = ["4H 7H 8H 9H 6H"]
    assert best_hands(hands) == expected


def test_flush_vs_full():
    hands = [
        "3H 6H 7H 8H 5H",
        "4S 5H 4C 5D 4H",
    ]
    expected = ["4S 5H 4C 5D 4H"]
    assert best_hands(hands) == expected


def test_two_fulls():
    hands = [
        "4H 4S 4D 9S 9D",
        "5H 5S 5D 8S 8D",
    ]
    expected = ["5H 5S 5D 8S 8D"]
    assert best_hands(hands) == expected


def test_two_fulls_same_triplet():
    hands = [
        "5H 5S 5D 9S 9D",
        "5H 5S 5D 8S 8D",
    ]
    expected = ["5H 5S 5D 9S 9D"]
    assert best_hands(hands) == expected


def test_full_vs_four():
    hands = [
        "4S 5H 4D 5D 4H",
        "3S 3H 2S 3D 3C",
    ]
    expected = ["3S 3H 2S 3D 3C"]
    assert best_hands(hands) == expected


def test_two_fours():
    hands = [
        "2S 2H 2C 8D 2D",
        "4S 5H 5S 5D 5C",
    ]
    expected = ["4S 5H 5S 5D 5C"]
    assert best_hands(hands) == expected


def test_two_fours_kicker():
    hands = [
        "3S 3H 2S 3D 3C",
        "3S 3H 4S 3D 3C",
    ]
    expected = ["3S 3H 4S 3D 3C"]
    assert best_hands(hands) == expected


def test_four_vs_straight_flush():
    hands = [
        "4S 5H 5S 5D 5C",
        "7S 8S 9S 6S 10S",
    ]
    expected = ["7S 8S 9S 6S 10S"]
    assert best_hands(hands) == expected


def test_two_straight_flushes():
    hands = [
        "4H 6H 7H 8H 5H",
        "5S 7S 8S 9S 6S",
    ]
    expected = ["5S 7S 8S 9S 6S"]
    assert best_hands(hands) == expected