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Quentin Ménoret
Quentin Ménoret

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Advent of code - Day 12

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.

Fun exercise today! I panicked a bit with that "angle" thing, but then I realised it was always 90°, which made it pretty straightforward.

Here is my solution for day #12:

const Command = {
  North: 'N',
  South: 'S',
  East: 'E',
  West: 'W',
  Left: 'L',
  Right: 'R',
  Forward: 'F',

function addTo(state, command, value) {
  if (command === Command.East) return { ...state, wpx: state.wpx + value }
  if (command === Command.West) return { ...state, wpx: state.wpx - value }
  if (command === Command.North) return { ...state, wpy: state.wpy - value }
  if (command === Command.South) return { ...state, wpy: state.wpy + value }

function rotate(state, command, param) {
  if (param === 0) return state
  if (command === Command.Left) return rotate({ ...state, wpy: 0 - state.wpx, wpx: state.wpy }, command, param - 90)
  if (command === Command.Right) return rotate({ ...state, wpx: 0 - state.wpy, wpy: state.wpx }, command, param - 90)

function execute([command, param], state) {
  if (command === Command.Forward) return { ...state, x: state.x + param * state.wpx, y: state.y + param * state.wpy }
  if (command === Command.Right || command === Command.Left) return rotate(state, command, param)
  return addTo(state, command, param)

const resultState = input.reduce(
  (state, command) => {
    return execute(command, state)
    x: 0,
    y: 0,
    wpx: 10,
    wpy: -1,
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Feel free to share your solution in the comments!

Photo by Markus Spiske on Unsplash

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