Advent of Code Day 5

day5.js

const puzzleInput = ``

// Part 1
const TOTAL_ROWS = 128
const TOTAL_COLS = 8

const parseInput = (input) => {
  return input.split('\n')
}

const binarySplit = (pos, high) => {
  const round = high ? Math.floor : Math.ceil
  const key = high ? 'min' : 'max'
  pos[key] = pos.max - round((pos.max - pos.min) / 2)
}

const getSeatPosition = (directions) => {
  const rowPos = {
    min: 0,
    max: TOTAL_ROWS - 1,
  }

  const colPos = {
    min: 0,
    max: TOTAL_COLS - 1,
  }

  directions.forEach(char => {
    switch (char) {
      case 'F': return binarySplit(rowPos, false)
      case 'B': return binarySplit(rowPos, true)
      case 'L': return binarySplit(colPos, false)
      case 'R': return binarySplit(colPos, true)
    }
  })

  return [rowPos.min, colPos.min]
}

const calcSeatId = (seat) => {
  const [row, col] = getSeatPosition(seat.split(''))
  return row * 8 + col
}

const partOne = (input) => {
  const seats = parseInput(input)
  const highestSeat = seats.reduce((acc, seat) => Math.max(acc, calcSeatId(seat)), 0)
  console.log(highestSeat)
}

partOne(puzzleInput)

// Part 2
const codeForPosition = (row, col) => {
  return `${row}:${col}`
}

const bothNeighborsFound = (lookup, row, col) => {
  return lookup[codeForPosition(row, col + 1)] && lookup[codeForPosition(row, col - 1)]
}

const partTwo = (input) => {
  const seatsLookup = {}
  parseInput(input).forEach((seat) => {
    const [row, col] = getSeatPosition(seat.split(''))
    seatsLookup[codeForPosition(row, col)] = [row, col]
  })

  const allSeats = []
  for (let i = 0; i < TOTAL_ROWS; i++) {
    for (let j = 0; j < TOTAL_COLS; j++) {
      allSeats.push([codeForPosition(i, j), i, j])
    }
  }

  const missingSeats = allSeats.filter(([code]) => !seatsLookup[code])
  const [myCode, myRow, myCol] = missingSeats.find(([code, row, col]) => bothNeighborsFound(seatsLookup, row, col))
  console.log(myRow * 8 + myCol)
}

partTwo(puzzleInput)