AdventOfCode-js-2024/1/1_2.js

import { loadInput } from "../common.js";

/** A dictionary to cache the counts of values from the right dictionary */
const _countDictionary = {};

// const input = loadInput("./1/test.input", parseInput, true);
const input = loadInput(1, parseInput);

solve(input);

/**
 * @param {string} inputData
 * @returns {number[][]}
 */
function parseInput(inputData) {
    // Split the input into lines, and then split each line into two numbers
    const lines = inputData.split(/\n/);
    let leftList = [];
    let rightList = [];

    // split each line into two numbers, then add those to the left and right lists
    for(const line of lines) {
        const [l, r] = line.split(/\s+/).map((num) => parseInt(num, 10));
        leftList.push(l);
        rightList.push(r);
    }

    return [leftList, rightList];
}

/**
 * @param {number[][]} parsedInput
 */
function solve(parsedInput) {
    // separate out the already sorted left and right list
    const [leftList, rightList] = parsedInput;
    // Create a list to store the differences between the left and right list
    const similarityValues = [];

    for(const left of leftList) {
        similarityValues.push(left * countFromRightList(left, rightList));
    }

    console.log("List Distance: ", eval(similarityValues.join("+")));
}

/**
 * Get a count of the number of times a value appears in the right list
 *
 * @param {number} numberToFind The number to get a count of
 * @param {number[]} rightList The list to search through to get a count of {@link numberToFind}
 *
 * @returns {number} The number of times {@link numberToFind} appears in the right list
 */
function countFromRightList(numberToFind, rightList) {
    if(_countDictionary[numberToFind]) {
        return _countDictionary[numberToFind];
    }

    const count = rightList.filter((value) => value == numberToFind).length;

    _countDictionary[numberToFind] = count;

    return count;
}