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Advent of code - Day 12

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.

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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