Advent of Code (AoC) 2023 Day 1 - Trebuchet?! - Solution in JavaScript

Other solutions: Day 2 Day 3

Solution for Advent of Code (AoC) 2023 Day 1: Trebuchet?! in JavaScript:

import fs from "fs";
import { log } from "console";

const lines = fs.readFileSync("./day1.txt", {encoding: "utf-8"}).split("\n");

function isDigit(char) {
  return /^\d$/.test(char);
}

function part1() {  
  let sum = 0;

  for (const line of lines) {
    let firstNum, lastNum;
    for (const c of line) {
      if (isDigit(c)) {
        if (!firstNum) {
          firstNum = c;
        }
        lastNum = c;
      }
    }

    const twoDigit = `${firstNum}${lastNum}`;
    sum += Number(twoDigit);
  }

  log(sum);
}

function part2() {
  let sum = 0;

  for(const line of lines) {
    let digits = [];

    for (let i = 0; i < line.length; i++) {
      const c = line[i];

      if (isDigit(c)) {
        digits.push(c);
      }

      const textDigits = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'];
      const lineSubstring = line.substring(i);
      for (let d = 0; d < textDigits.length; d++) {
        const textDigit = textDigits[d];
        if (lineSubstring.startsWith(textDigit)) {
          digits.push(d+1);
        }
      }
    }

    const lastIndex = digits.length - 1;
    const twoDigits = `${digits[0]}${digits[lastIndex]}`;

    sum += Number(twoDigits);
  }

  log(sum);
}

part1();
part2();