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Advent of code - Day 25

qmenoret profile image Quentin Ménoret ・2 min read

Are you participating in the Advent of code this year?

If you don't know what the advent of code is, it's a website where you'll find a daily challenge (every day it gets harder). It's a really fun event, you should participate!

I try to solve the exercises using either JavaScript or TypeScript and will share my solutions daily (with one day delay so no one can cheat!). I only share the solution for the second part.


And it's the last day of the event! For this one, Advent of Code was merciful. It only takes a few minutes to complete with a simple loop.

All in all this year challenges were great. A few were really complex and interesting, I really encourage you to try it out! But I'm honestly happy that it's over so I can relax and enjoy some time of. Completing all the challenges the day of the release takes time and commitment, I'm really proud I managed to keep up with the game!

Here is my solution for day #25:

function transform(subjectNumber: number, value: number) {
  return (value * subjectNumber) % 20201227
}

function getLoopSize(id: number) {
  let current = 7
  let iterations = 1
  while (current !== id) {
    current = transform(7, current)
    iterations++
  }
  return iterations
}

const card = getLoopSize(10943862)
console.log({ card })
const door = getLoopSize(12721030)
console.log({ door })

let resultFromDoor = 12721030
for (let i = 0; i < card - 1; i++) {
  resultFromDoor = transform(12721030, resultFromDoor)
}

console.log(resultFromDoor)

let resultFromCard = 10943862
for (let i = 0; i < door - 1; i++) {
  resultFromCard = transform(10943862, resultFromCard)
}

console.log(resultFromCard)
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Feel free to share your solution in the comments!


Photo by Markus Spiske on Unsplash

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