124 lines
6.8 KiB
Plaintext
124 lines
6.8 KiB
Plaintext
Advent of Code
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br0xen (AoC++) 8*
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--- Day 4: Scratchcards ---
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The gondola takes you up. Strangely, though, the ground doesn't seem to be 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 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 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 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?" You ask about water sources.
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"I'm not sure; I just operate the gondola lift. That does sound like something we'd have, though - this is Island Island, after all! I bet the gardener
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would know. He's on a different island, though - er, the small kind surrounded by water, not the floating kind. We really need to come up with a better
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naming scheme. Tell you what: if you can help me with something quick, I'll let you borrow my boat and you can go visit the gardener. I got all these
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scratchcards 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 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 a vertical bar (|): a list of winning numbers and then a list of numbers
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you 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 the numbers you have appear in the list of winning numbers. The first
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match makes the card worth one point and each match after the first doubles the 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) and eight numbers you have (83, 86, 6, 31, 17, 9, 48, and 53). Of the
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numbers you have, four of them (48, 83, 17, and 86) are winning numbers! That means card 1 is worth 8 points (1 for the first match, then doubled three
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times for 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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Your puzzle answer was 21158.
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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 that the rules have actually been printed on the back of every card this
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whole time.
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There's no such thing as "points". Instead, scratchcards only cause you to win 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 to the number of matches. So, if card 10 were to have 5 matching numbers,
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you 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 card number as the card they copied. So, if you win a copy of card 10 and
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it has 5 matching numbers, it would then win a copy of the same cards that the original card 10 won: cards 11, 12, 13, 14, and 15. This process repeats
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until none of the copies cause you to win any more cards. (Cards will never make you 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 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 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 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 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 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 wins no more cards.
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Once all of the originals and copies have been processed, you end up with 1 instance of card 1, 2 instances of card 2, 4 instances of card 3, 8
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instances of card 4, 14 instances of card 5, and 1 instance of card 6. In total, this example pile of scratchcards causes you to ultimately have 30
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scratchcards!
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Process all of the original and copied scratchcards until no more scratchcards 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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Your puzzle answer was 6050769.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should return to your Advent calendar and try another puzzle.
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If you still want to see it, you can get your puzzle input.
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You can also [Shareon Twitter Mastodon] this puzzle.
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References
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Visible links
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. https://adventofcode.com/
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. https://adventofcode.com/2023/about
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. https://adventofcode.com/2023/events
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. https://teespring.com/stores/advent-of-code
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. https://adventofcode.com/2023/settings
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. https://adventofcode.com/2023/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2023/support
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. https://adventofcode.com/2023
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. https://adventofcode.com/2023
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. https://adventofcode.com/2023/support
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. https://adventofcode.com/2023/sponsors
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. https://adventofcode.com/2023/leaderboard
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. https://adventofcode.com/2023/stats
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. https://adventofcode.com/2023/sponsors
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. https://en.wikipedia.org/wiki/Scratchcard
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. https://adventofcode.com/2023
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. https://adventofcode.com/2023/day/4/input
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