import 2023 aoc

2023/day7/day7.py

@@ -0,0 +1,70 @@
+from collections import Counter
+
+
+def calculate_rank(hand, part2=False):
+    card_ranks = {'2': 1, '3': 2, '4': 3, '5': 4, '6': 5, '7': 6, '8': 7, '9': 8, 'T': 9, 'J': 10, 'Q': 11, 'K': 12, 'A': 13}
+    if part2:
+        # in part2, jokers are the weakest card
+        card_ranks['J'] = 0
+    # substitute cards with their ranks to make them sortable
+    hand = [card_ranks[c] for c in hand]
+    cnt = Counter(hand)
+    
+    if part2 and cnt[0] != 5:  # edge case if hand == 'JJJJJ'
+        # substitute jokers with the most common card that isn't a joker
+        most_common_card = cnt.most_common(2)[0][0] if cnt.most_common(2)[0][0] != 0 else cnt.most_common(2)[1][0]
+        new_hand = [most_common_card if c == 0 else c for c in hand]
+        cnt = Counter(new_hand)
+    
+    rank = 0
+    match sorted(cnt.values()):
+        case [5]: rank = 7
+        case [1, 4]: rank = 6
+        case [2, 3]: rank = 5
+        case [1, 1, 3]: rank = 4
+        case [1, 2, 2]: rank = 3
+        case [1, 1, 1, 2]: rank = 2
+        case [1, 1, 1, 1, 1]: rank = 1
+    # return rank, and hand as a tiebreaker
+    return (rank, hand)
+
+def parse_input(inp):
+    hands = [l.strip().split() for l in inp.strip().split("\n")]
+    return hands
+
+
+def calculate_wins(hands, part2=False):
+    total = 0
+    hands = sorted(hands, key=lambda hb: calculate_rank(hb[0], part2=part2))
+    for rank, hand in enumerate(hands):
+        hand, bid = hand
+        total += (rank + 1) * int(bid)
+    return total
+
+
+if __name__ == "__main__":
+    sample_input = """
+        32T3K 765
+        T55J5 684
+        KK677 28
+        KTJJT 220
+        QQQJA 483
+    """
+    res = calculate_wins(parse_input(sample_input))
+    print(f"part 1 example: {res}")
+    assert res == 6440
+
+    res = calculate_wins(parse_input(sample_input), part2=True)
+    print(f"part 2 example: {res}")
+    assert res == 5905
+    
+    import sys
+    if len(sys.argv) == 2:
+        with open(sys.argv[1]) as f:
+            inp = parse_input(f.read())
+            
+            res = calculate_wins(inp)
+            print(f"Part 1, res={res}")
+            
+            res = calculate_wins(inp, part2=True)
+            print(f"Part 2, res={res}")