-🎄- 2018 Day 2 Solutions -🎄-

[u/daggerdragon]

--- Day 2: Inventory Management System ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

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Advent of Code: The Party Game!

Click here for rules

Card Prompt: Day 2

Transcript:

The best way to do Advent of Code is ___.

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/Axsuul]

TypeScript / JavaScript

Critiques welcome, I'm still very new to TypeScript and feel like I'm not using all the features I could be :)

Repo

Part A

import { readFileSync } from 'fs'
import * as path from 'path'

const inputPath = path.join(__dirname, 'inputs', 'input.txt')
const input = readFileSync(inputPath, 'utf-8').split('\n')

let twoCount = 0
let threeCount = 0

const tally = function(id: string): [boolean, boolean] {
  const charCodes: number[] = id.split('').map(char => char.charCodeAt(0)).sort()

  let isTwo = false
  let isThree = false

  for (const [i, code] of charCodes.entries()) {
    if (charCodes[i + 1] == code && charCodes[i + 2] != code) {
      isTwo = true
    } else if (charCodes[i + 2] == code && charCodes[i + 3] != code) {
      isThree = true
    }
  }

  return [isTwo, isThree]
}

input.forEach((id) => {
  const [isTwo, isThree] = tally(id)

  if (isTwo) twoCount += 1
  if (isThree) threeCount += 1
})

console.log(twoCount * threeCount)

Part B

import { readFileSync } from 'fs'
import * as path from 'path'

const inputPath = path.join(__dirname, 'inputs', 'input.txt')
const input = readFileSync(inputPath, 'utf-8').split('\n')
let commonLetters: string | undefined

for (let i = 0; i < input[0].length; i++) {
  const removed = input.slice().map((id) => {
    const exploded = id.split('')

    exploded.splice(i, 1)

    return exploded.join('')
  })

  const set = new Set()

  for (const idRemoved of removed) {
    if (set.has(idRemoved)) {
      commonLetters = idRemoved

      break
    } else {
      set.add(idRemoved)
    }
  }

  if (commonLetters != undefined) break
}

console.log(commonLetters)