111 lines
4.3 KiB
Plaintext
111 lines
4.3 KiB
Plaintext
Advent of Code
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br0xen (AoC++) 6*
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--- Day 3: Gear Ratios ---
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You and the Elf eventually reach a gondola lift station; he says the gondola lift will take you up to the water source, but
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this is as far as he can bring you. You go inside.
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It doesn't take long to find the gondolas, but there seems to be a problem: they're not moving.
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"Aaah!"
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You turn around to see a slightly-greasy Elf with a wrench and a look of surprise. "Sorry, I wasn't expecting anyone! The
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gondola lift isn't working right now; it'll still be a while before I can fix it." You offer to help.
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The engineer explains that an engine part seems to be missing from the engine, but nobody can figure out which one. If you
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can add up all the part numbers in the engine schematic, it should be easy to work out which part is missing.
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The engine schematic (your puzzle input) consists of a visual representation of the engine. There are lots of numbers and
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symbols you don't really understand, but apparently any number adjacent to a symbol, even diagonally, is a "part number"
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and should be included in your sum. (Periods (.) do not count as a symbol.)
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Here is an example engine schematic:
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467..114..
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...*......
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..35..633.
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......#...
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617*......
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.....+.58.
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..592.....
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......755.
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...$.*....
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.664.598..
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In this schematic, two numbers are not part numbers because they are not adjacent to a symbol: 114 (top right) and 58
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(middle right). Every other number is adjacent to a symbol and so is a part number; their sum is 4361.
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Of course, the actual engine schematic is much larger. What is the sum of all of the part numbers in the engine schematic?
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Your puzzle answer was 543867.
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--- Part Two ---
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The engineer finds the missing part and installs it in the engine! As the engine springs to life, you jump in the closest
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gondola, finally ready to ascend to the water source.
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You don't seem to be going very fast, though. Maybe something is still wrong? Fortunately, the gondola has a phone labeled
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"help", so you pick it up and the engineer answers.
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Before you can explain the situation, she suggests that you look out the window. There stands the engineer, holding a phone
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in one hand and waving with the other. You're going so slowly that you haven't even left the station. You exit the gondola.
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The missing part wasn't the only issue - one of the gears in the engine is wrong. A gear is any * symbol that is adjacent
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to exactly two part numbers. Its gear ratio is the result of multiplying those two numbers together.
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This time, you need to find the gear ratio of every gear and add them all up so that the engineer can figure out which gear
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needs to be replaced.
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Consider the same engine schematic again:
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467..114..
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...*......
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..35..633.
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......#...
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617*......
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.....+.58.
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..592.....
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......755.
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...$.*....
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.664.598..
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In this schematic, there are two gears. The first is in the top left; it has part numbers 467 and 35, so its gear ratio is
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16345. The second gear is in the lower right; its gear ratio is 451490. (The * adjacent to 617 is not a gear because it is
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only adjacent to one part number.) Adding up all of the gear ratios produces 467835.
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What is the sum of all of the gear ratios in your engine schematic?
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Your puzzle answer was 79613331.
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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/Gondola_lift
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. https://adventofcode.com/2023
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. https://adventofcode.com/2023/day/3/input
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