160 lines
6.7 KiB
Python
160 lines
6.7 KiB
Python
# --- Day 4: Scratchcards ---
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# The gondola takes you up. Strangely, though, the ground doesn't seem to be
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# coming with you; you're not climbing a mountain. As the circle of Snow Island
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# recedes below you, an entire new landmass suddenly appears above you! The
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# gondola carries you to the surface of the new island and lurches into the
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# station.
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# As you exit the gondola, the first thing you notice is that the air here is
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# much warmer than it was on Snow Island. It's also quite humid. Is this where
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# the water source is?
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# The next thing you notice is an Elf sitting on the floor across the station in
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# what seems to be a pile of colorful square cards.
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# "Oh! Hello!" The Elf excitedly runs over to you. "How may I be of service?"
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# You ask about water sources.
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# "I'm not sure; I just operate the gondola lift. That does sound like something
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# we'd have, though - this is Island Island, after all! I bet the gardener would
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# know. He's on a different island, though - er, the small kind surrounded by
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# water, not the floating kind. We really need to come up with a better naming
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# scheme. Tell you what: if you can help me with something quick, I'll let you
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# borrow my boat and you can go visit the gardener. I got all these scratchcards
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# as a gift, but I can't figure out what I've won."
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# The Elf leads you over to the pile of colorful cards. There, you discover
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# dozens of scratchcards, all with their opaque covering already scratched off.
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# Picking one up, it looks like each card has two lists of numbers separated by
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# a vertical bar (|): a list of winning numbers and then a list of numbers you
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# have. You organize the information into a table (your puzzle input).
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# As far as the Elf has been able to figure out, you have to figure out which of
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# the numbers you have appear in the list of winning numbers. The first match
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# makes the card worth one point and each match after the first doubles the
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# point value of that card.
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# For example:
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# Card 1: 41 48 83 86 17 | 83 86 6 31 17 9 48 53
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# Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
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# Card 3: 1 21 53 59 44 | 69 82 63 72 16 21 14 1
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# Card 4: 41 92 73 84 69 | 59 84 76 51 58 5 54 83
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# Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
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# Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
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# In the above example, card 1 has five winning numbers (41, 48, 83, 86, and 17)
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# and eight numbers you have (83, 86, 6, 31, 17, 9, 48, and 53). Of the numbers
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# you have, four of them (48, 83, 17, and 86) are winning numbers! That means
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# card 1 is worth 8 points (1 for the first match, then doubled three times for
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# each of the three matches after the first).
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# Card 2 has two winning numbers (32 and 61), so it is worth 2 points.
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# Card 3 has two winning numbers (1 and 21), so it is worth 2 points.
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# Card 4 has one winning number (84), so it is worth 1 point.
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# Card 5 has no winning numbers, so it is worth no points.
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# Card 6 has no winning numbers, so it is worth no points.
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# So, in this example, the Elf's pile of scratchcards is worth 13 points.
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# Take a seat in the large pile of colorful cards. How many points are they worth in total?
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with open("files/P4.txt") as f:
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cards = [line for line in f.read().strip().split("\n")]
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def part1():
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total = 0
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for card in cards:
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game = card.split(":")[1].split("|")
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winning = set(int(n) for n in game[0].split())
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hand = set(int(n) for n in game[1].split())
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winners = list(winning & hand)
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if (winning_hand := len(winners)) == 1:
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total += 1
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if winning_hand > 1:
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total += pow(2, winning_hand - 1)
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print(f"There are {total} points in total")
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# --- Part Two ---
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# Just as you're about to report your findings to the Elf, one of you realizes
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# that the rules have actually been printed on the back of every card this whole
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# time.
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# There's no such thing as "points". Instead, scratchcards only cause you to win
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# more scratchcards equal to the number of winning numbers you have.
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# Specifically, you win copies of the scratchcards below the winning card equal
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# to the number of matches. So, if card 10 were to have 5 matching numbers, you
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# would win one copy each of cards 11, 12, 13, 14, and 15.
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# Copies of scratchcards are scored like normal scratchcards and have the same
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# card number as the card they copied. So, if you win a copy of card 10 and it
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# has 5 matching numbers, it would then win a copy of the same cards that the
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# original card 10 won: cards 11, 12, 13, 14, and 15. This process repeats until
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# none of the copies cause you to win any more cards. (Cards will never make you
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# copy a card past the end of the table.)
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# This time, the above example goes differently:
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# Card 1: 41 48 83 86 17 | 83 86 6 31 17 9 48 53
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# Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
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# Card 3: 1 21 53 59 44 | 69 82 63 72 16 21 14 1
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# Card 4: 41 92 73 84 69 | 59 84 76 51 58 5 54 83
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# Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
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# Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
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# Card 1 has four matching numbers, so you win one copy each of the next
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# four cards: cards 2, 3, 4, and 5.
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# Your original card 2 has two matching numbers, so you win one copy each of
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# cards 3 and 4.
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# Your copy of card 2 also wins one copy each of cards 3 and 4.
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# Your four instances of card 3 (one original and three copies) have two
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# matching numbers, so you win four copies each of cards 4 and 5.
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# Your eight instances of card 4 (one original and seven copies) have one
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# matching number, so you win eight copies of card 5.
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# Your fourteen instances of card 5 (one original and thirteen copies) have
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# no matching numbers and win no more cards.
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# Your one instance of card 6 (one original) has no matching numbers and
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# wins no more cards.
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# Once all of the originals and copies have been processed, you end up with 1
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# instance of card 1, 2 instances of card 2, 4 instances of card 3, 8 instances
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# of card 4, 14 instances of card 5, and 1 instance of card 6. In total, this
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# example pile of scratchcards causes you to ultimately have 30 scratchcards!
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# Process all of the original and copied scratchcards until no more scratchcards
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# are won. Including the original set of scratchcards, how many total
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# scratchcards do you end up with?
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from collections import defaultdict
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score = defaultdict(int)
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def part2():
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for idx, card in enumerate(cards):
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game = card.split(":")[1].split("|")
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winning = set(int(n) for n in game[0].split())
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hand = set(int(n) for n in game[1].split())
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winners = list(winning & hand)
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score[idx] += 1
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for i, _ in enumerate(winners):
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score[idx + 1 + i] += score[idx]
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print(f"There are {sum(score.values())} scratchcards")
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if __name__ == "__main__":
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part1()
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part2()
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