From 006f94b97d1f89602b45fe2ab2fb80bf59165874 Mon Sep 17 00:00:00 2001 From: zenon Date: Sun, 1 Dec 2019 19:08:41 +0100 Subject: [PATCH] Add task description --- day1/README.md | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 day1/README.md diff --git a/day1/README.md b/day1/README.md new file mode 100644 index 0000000..4859425 --- /dev/null +++ b/day1/README.md @@ -0,0 +1,72 @@ +# Day1: The Tyranny of the Rocket Equation + +## Problem + +### Part One + +Santa has become stranded at the edge of the Solar System while delivering +presents to other planets! To accurately calculate his position in space, +safely align his warp drive, and return to Earth in time to save Christmas, he +needs you to bring him measurements from fifty stars. + +Collect stars by solving puzzles. Two puzzles will be made available on each +day in the Advent calendar; the second puzzle is unlocked when you complete the +first. Each puzzle grants one star. Good luck! + +The Elves quickly load you into a spacecraft and prepare to launch. + +At the first Go / No Go poll, every Elf is Go until the Fuel Counter-Upper. +They haven't determined the amount of fuel required yet. + +Fuel required to launch a given module is based on its mass. Specifically, to +find the fuel required for a module, take its mass, divide by three, round +down, and subtract 2. + +For example: + +* For a mass of 12, divide by 3 and round down to get 4, then subtract 2 to +get 2. +* For a mass of 14, dividing by 3 and rounding down still yields 4, so +the fuel required is also 2. +* For a mass of 1969, the fuel required is 654. +* For a mass of 100756, the fuel required is 33583. + +The Fuel Counter-Upper needs to know the total fuel requirement. To find it, +individually calculate the fuel needed for the mass of each module (your puzzle +input), then add together all the fuel values. + +What is the sum of the fuel requirements for all of the modules on your +spacecraft? + +### Part Two + +During the second Go / No Go poll, the Elf in charge of the Rocket Equation +Double-Checker stops the launch sequence. Apparently, you forgot to include +additional fuel for the fuel you just added. + +Fuel itself requires fuel just like a module - take its mass, divide by three, +round down, and subtract 2. However, that fuel also requires fuel, and that +fuel requires fuel, and so on. Any mass that would require negative fuel should +instead be treated as if it requires zero fuel; the remaining mass, if any, is +instead handled by wishing really hard, which has no mass and is outside the +scope of this calculation. + +So, for each module mass, calculate its fuel and add it to the total. Then, +treat the fuel amount you just calculated as the input mass and repeat the +process, continuing until a fuel requirement is zero or negative. For example: + +* A module of mass 14 requires 2 fuel. This fuel requires no further fuel (2 + divided by 3 and rounded down is 0, which would call for a negative fuel), so + the total fuel required is still just 2. +* At first, a module of mass 1969 + requires 654 fuel. Then, this fuel requires 216 more fuel (654 / 3 - 2). 216 + then requires 70 more fuel, which requires 21 fuel, which requires 5 fuel, + which requires no further fuel. So, the total fuel required for a module of + mass 1969 is 654 + 216 + 70 + 21 + 5 = 966. +* The fuel required by a module of mass 100756 and its fuel is: 33583 + 11192 + + 3728 + 1240 + 411 + 135 + 43 + 12 + 2 = 50346. + +What is the sum of the fuel requirements for all of the modules on your +spacecraft when also taking into account the mass of the added fuel? (Calculate +the fuel requirements for each module separately, then add them all up at the +end.)