89 lines
4.1 KiB
Plaintext
89 lines
4.1 KiB
Plaintext
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Advent of Code
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--- Day 1: The Tyranny of the Rocket Equation ---
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Santa has become stranded at the edge of the Solar System while delivering presents
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to other planets! To accurately calculate his position in space, safely align his
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warp drive, and return to Earth in time to save Christmas, he needs you to bring
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him measurements from fifty stars.
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Collect stars by solving puzzles. Two puzzles will be made available on each day in
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the Advent calendar; the second puzzle is unlocked when you complete the first.
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Each puzzle grants one star. Good luck!
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The Elves quickly load you into a spacecraft and prepare to launch.
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At the first Go / No Go poll, every Elf is Go until the Fuel Counter-Upper. They
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haven't determined the amount of fuel required yet.
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Fuel required to launch a given module is based on its mass. Specifically, to find
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the fuel required for a module, take its mass, divide by three, round down, and
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subtract 2.
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For example:
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* For a mass of 12, divide by 3 and round down to get 4, then subtract 2 to get
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2.
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* For a mass of 14, dividing by 3 and rounding down still yields 4, so the fuel
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required is also 2.
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* For a mass of 1969, the fuel required is 654.
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* For a mass of 100756, the fuel required is 33583.
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The Fuel Counter-Upper needs to know the total fuel requirement. To find it,
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individually calculate the fuel needed for the mass of each module (your puzzle
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input), then add together all the fuel values.
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What is the sum of the fuel requirements for all of the modules on your spacecraft?
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The first half of this puzzle is complete! It provides one gold star: *
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--- Part Two ---
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During the second Go / No Go poll, the Elf in charge of the Rocket Equation
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Double-Checker stops the launch sequence. Apparently, you forgot to include
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additional fuel for the fuel you just added.
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Fuel itself requires fuel just like a module - take its mass, divide by three,
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round down, and subtract 2. However, that fuel also requires fuel, and that fuel
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requires fuel, and so on. Any mass that would require negative fuel should instead
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be treated as if it requires zero fuel; the remaining mass, if any, is instead
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handled by wishing really hard, which has no mass and is outside the scope of this
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calculation.
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So, for each module mass, calculate its fuel and add it to the total. Then, treat
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the fuel amount you just calculated as the input mass and repeat the process,
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continuing until a fuel requirement is zero or negative. For example:
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* A module of mass 14 requires 2 fuel. This fuel requires no further fuel (2
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divided by 3 and rounded down is 0, which would call for a negative fuel), so
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the total fuel required is still just 2.
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* At first, a module of mass 1969 requires 654 fuel. Then, this fuel requires 216
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more fuel (654 / 3 - 2). 216 then requires 70 more fuel, which requires 21
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fuel, which requires 5 fuel, which requires no further fuel. So, the total fuel
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required for a module of mass 1969 is 654 + 216 + 70 + 21 + 5 = 966.
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* The fuel required by a module of mass 100756 and its fuel is: 33583 + 11192 +
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3728 + 1240 + 411 + 135 + 43 + 12 + 2 = 50346.
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What is the sum of the fuel requirements for all of the modules on your spacecraft
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when also taking into account the mass of the added fuel? (Calculate the fuel
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requirements for each module separately, then add them all up at the end.)
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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/2019/about
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. https://adventofcode.com/2019/events
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. https://adventofcode.com/2019/settings
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. https://adventofcode.com/2019/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2019/support
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. https://adventofcode.com/2019
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. https://adventofcode.com/2019
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. https://adventofcode.com/2019/support
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. https://adventofcode.com/2019/sponsors
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. https://adventofcode.com/2019/leaderboard
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. https://adventofcode.com/2019/stats
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. https://adventofcode.com/2019/sponsors
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. https://adventofcode.com/2019/day/1/input
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