Advent of Code 2020 Day 5 TypeScript

day5.ts

import { readFileSync } from 'fs';

const findRowNumber = (address: string, lowerBoundary: number, upperBoundary: number): number => {
    if (!address.length) {
        return lowerBoundary;
    }

    const remainingAddress = address.slice(1);
    const distance = ((upperBoundary - lowerBoundary) / 2);
    if (address[0] === 'F' || address[0] === 'L') {
        upperBoundary = Math.floor(upperBoundary - distance);
    } else {
        lowerBoundary = Math.ceil(lowerBoundary + distance);
    }

    return findRowNumber(remainingAddress, lowerBoundary, upperBoundary);
};

const getSeatId = (address: string) => {
    const rowNumber = findRowNumber(address.slice(0, 7), 0, 127);
    const colNumber = findRowNumber(address.slice(7), 0, 7);
    return (rowNumber * 8) + colNumber;
};

const findSurroundedSeat = (seatIds: number[]) => {
    for (let i = 0; i < seatIds.length - 2; i++) {
        if (seatIds[i + 2] - seatIds[i] !== 2) {
            return (seatIds[i + 1] + 1);
        }
    }
}

const boardingPasses = readFileSync('input.txt').toString('utf8').split('\n');
const seatIds = boardingPasses.map(bp => getSeatId(bp));

console.log(`Chapter 1: ${Math.max(...seatIds)}`);

seatIds.sort((a, b) => a - b)

console.log(`Chapter 2 : ${findSurroundedSeat(seatIds)}`);