script.js

'use strict'
// Setup

const getSeatIDs = boardingPasses => {
    return boardingPasses.split('\n')
        .map(boardingPass => {
            return parseInt(boardingPass.replace(/F|L/g, '0').replace(/B|R/g, '1'), 2)
        })
}

// Part 1
// ======

const part1 = input => {

    return getSeatIDs(input)
        .sort((a, b) => b - a)
        .shift()

}

// Part 2
// ======

const part2 = input => {
    const seats = getSeatIDs(input)
        .sort((a, b) => a - b)

    const minSeat = seats[0]
    const maxSeat = seats[seats.length - 1]
    for (var seat = minSeat; seat < maxSeat; seat++) {
        if (!seats.includes(seat)) return seat
    }
}

const part3 = input => {
    return parseInt(input).toString(2)
        .padStart(10, '0')
        .replace(/^((?:0|1){7})((?:0|1){3})$/, (match, row, col) => {
            return row.replace(/1/g, 'B').replace(/0/g, 'F') + col.replace(/1/g, 'R').replace(/0/g, 'L')
        })
}

module.exports = { part1, part2, part3 }

//12:00 AM - start
//12:18 AM - getRange method 
//12:21 AM - part 1
//12:23 AM - part 2