Advent Of Code @programming.dev zerodivision @mander.xyz 11mo ago

[2023 Day 7] Part 2 poorly specified

The instructions for part 2 are missing info about how to handle the Four Of A Kind and a joker case. Wasted quite some time because I assumed that the remaining joker would remain unused, but turns out it turns your deck into Five Of A Kind.

Did everybody else just expect this?

5 comments

Why would the joker remain unused? The problem clearly says joker acts as the card that makes the hand strongest, so in this case, 5 of a kind.
There are no suits in this game, so no limit of how many cards of a same kind can be in a hand. Five of a kind is explicitly mentioned in the rules of the game.
- Oh oh, you're correct :( How did I not notice that; guess too much thinking about standard card games, plus no hand in the example input is a Five Of A Kind.
For part 2, the only thing that I missed at first was the JJJJJ edge case. My approach was:

count the amount of jokers

remove them from the hand

count the rest

add the amount of jokers to the biggest set in the hand

Last step fails if there are no other cards left after you remove the jokers...

Here's a (hopefully correct) solution (in Python) where a Five Of A Kind hand is not allowed:

Code

i = open('day7_in.txt')

from collections import Counter

card_values = {
    'A': 14,
    'K': 13,
    'Q': 12,
    'J': 0,
    'T': 10
}

deques = []

for line in i:
    if not line.strip():
        continue
    cards, bid = line.split()
    cards_repr = [int(card_values.get(card, card)) for card in cards]
    counts = Counter(card for card in cards if card != 'J')
    deque_type = [times for card, times in counts.most_common(5)]

    jokers_left = cards.count('J')
    for i in range(jokers_left):
        for j, n in enumerate(deque_type):
            if n &lt; 4:
                deque_type[j] += 1
                jokers_left -= 1
                break
    if jokers_left:
        if jokers_left &lt;= 4:
            deque_type.append(jokers_left)
        else:
            deque_type += [4, 1]
    deques.append((deque_type, cards_repr, int(bid), cards))

deques.sort()

ans = 0
for n, d in enumerate(deques, 1):
    ans += n*d[2]

print(ans)