Day1.js

import { readFileSync } from 'node:fs';
import * as math from 'mathjs';
// Reading in the input file
const inputFile = readFileSync('../../AdventOfCode_inputs/day1_input.txt')
const fileSplit = inputFile.toString().split('\n')
// Sort file into left and right column lists
var leftColumn = [];
var rightColumn = [];
fileSplit.forEach(line => {
    leftColumn.push(Number(line.split(/\s+/)[0]));
    rightColumn.push(Number(line.split(/\s+/)[1]));
})

function sortDistance(leftColumn, rightColumn) {
    // First sort the two columns from smallest to largest
    // then calculate and sum the distances between the two columns
    leftColumn.sort();
    rightColumn.sort();
    const negRightColumn = rightColumn.map(x => -x);
    const difference = math.add(leftColumn, negRightColumn);
    return math.sum(math.abs(difference));
}

function similarityScore(leftColumn, rightColumn) {
    var similarity = 0;
    leftColumn.forEach(element => {
        // Count how many times the element from leftColumn appears in rightColumn
        var amount = rightColumn.filter((currentItem) => currentItem == element).length;
        similarity += element * amount;
    })
    return similarity;
}

console.log(sortDistance(leftColumn, rightColumn));
console.log(similarityScore(leftColumn, rightColumn));