AoC Day 3

aoc_3_part1.ts

import * as fs from "fs";

const lines: string[] = fs.readFileSync("input.txt", "utf-8").split("\n");
let numbersList = getNumbers();

let count = 0;
countValidNumbers(numbersList);

console.log(count);

function getNumbers() {
  let numbersList: Number[] = [];
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    const numberPattern = /\d+/g;
    let match;
    while ((match = numberPattern.exec(line)) !== null) {
      const foundItem: Number = {
        number: parseInt(match[0]),
        start: match.index,
        end: match.index + match[0].length,
        line,
        lineNumber: i,
      };
      numbersList.push(foundItem);
    }
  }
  return numbersList;
}

function countValidNumbers(numbersList: Number[]) {
  for (const number of numbersList) {
    const currentLine = number.line;

    let previousLine;
    if (number.lineNumber === 0) {
      previousLine = null;
    } else {
      previousLine = lines[number.lineNumber - 1];
    }

    let nextLine;
    if (number.lineNumber === lines.length - 1) {
      nextLine = null;
    } else {
      nextLine = lines[number.lineNumber + 1];
    }

    // check same line symbols
    if (
      (number.start > 0 && isSymbol(currentLine[number.start - 1])) ||
      isSymbol(currentLine[number.end])
    ) {
      count += number.number;
      continue;
    }
    //check above and below line symbols
    for (let i = number.start - 1; i <= number.end; i++) {
      if (i >= currentLine.length || i < 0) {
        continue;
      }
      if (
        (previousLine !== null && isSymbol(previousLine[i])) ||
        (nextLine !== null && isSymbol(nextLine[i]))
      ) {
        count += number.number;
        break;
      }
    }
  }
}

function isSymbol(char: string) {
  if (char.match(/\d/) || char === "." || char === "\r") {
    return false;
  }
  return true;
}

type Number = {
  number: number;
  start: number;
  end: number;
  line: string;
  lineNumber: number;
};

aoc_3_part2.ts

import * as fs from "fs";

let count = 0;
const lines: string[] = fs.readFileSync("input.txt", "utf-8").split("\n");
let numbersList = getNumbers();
let starsList = getStars();
countGears();
console.log(count);

function getNumbers(): NumberItem[] {
  const numberPattern = /\d+/g;
  return lines.flatMap((line, lineNumber) => {
    let matches = Array.from(line.matchAll(numberPattern));
    let numbersList: NumberItem[] = [];
    if (!matches) {
      return numbersList;
    }
    matches.forEach((match) => {
      const foundItem: NumberItem = {
        number: parseInt(match[0]),
        start: match.index ?? 0,
        end: (match.index ?? 0) + match[0].length - 1,
        line,
        lineNumber: lineNumber,
      };
      numbersList.push(foundItem);
    });
    return numbersList;
  });
}
function getStars() {
  let starsList: Star[] = [];
  for (let i = 0; i < lines.length; i++) {
    let line = lines[i];
    for (let j = 0; j < line.length; j++) {
      if (line[j] === "*") {
        let star: Star = {
          position: j,
          line: line,
          lineNumber: i,
        };
        starsList.push(star);
      }
    }
  }
  return starsList;
}
function countGears() {
  for (const star of starsList) {
    //get numbers that are below, above or on the same line
    //if position of any of their digit aligns with any position we look for we add it to the list
    let adjacentNumbers = numbersList.filter(
      (number) =>
        [star.lineNumber - 1, star.lineNumber, star.lineNumber + 1].includes(
          number.lineNumber
        ) &&
        createArray(number.start, number.end).some((value) =>
          [star.position - 1, star.position, star.position + 1].includes(value)
        )
    );

    if (adjacentNumbers.length === 2) {
      count += adjacentNumbers[0].number * adjacentNumbers[1].number;
    }
  }
}

function createArray(start: number, end: number) {
  const result: number[] = [];

  for (let i = start; i <= end; i++) {
    result.push(i);
  }

  return result;
}
type NumberItem = {
  number: number;
  start: number;
  end: number;
  line: string;
  lineNumber: number;
};

type Star = {
  position: number;
  line: string;
  lineNumber: number;
};