AoC 2024 day 5

const fs = require("fs")

const input = fs.readFileSync(__dirname + (process.argv.includes("--test") ? "/test.txt" : "/input.txt"), "utf8")

const parseInput = (rawInput) => {
    const [rulesSection, updatesSection] = rawInput.replace(/\r\n/g, "\n").split("\n\n")
    const rules = rulesSection.split("\n").map((line) => line.split("|").map(Number))
    const updates = updatesSection.split("\n").map((line) => line.split(",").map(Number))
    return { rules, updates }
}

const isUpdateInOrder = (update, rules) => {
    for (const [before, after] of rules) {
        const beforeIndex = update.indexOf(before)
        const afterIndex = update.indexOf(after)
        if (beforeIndex !== -1 && afterIndex !== -1 && beforeIndex > afterIndex) {
            return false
        }
    }
    return true
}

const getMiddlePage = (update) => update[Math.floor(update.length / 2)]

const reorderUpdate = (update, rules) => {
    const ruleMap = new Map()
    for (const [a, b] of rules) {
        if (!ruleMap.has(b)) ruleMap.set(b, new Set())
        ruleMap.get(b).add(a)
    }

    return update.slice().sort((a, b) => {
        if (ruleMap.get(a)?.has(b)) return 1
        if (ruleMap.get(b)?.has(a)) return -1
        return 0
    })
}

const part1 = ({ rules, updates }) =>
    updates
        .filter((update) => isUpdateInOrder(update, rules))
        .map(getMiddlePage)
        .reduce((sum, middle) => sum + middle, 0)

const part2 = ({ rules, updates }) =>
    updates
        .filter((update) => !isUpdateInOrder(update, rules))
        .map((update) => reorderUpdate(update, rules))
        .map(getMiddlePage)
        .reduce((sum, middle) => sum + middle, 0)

const data = parseInput(input)

console.time("Part 1 Time")
console.log("Part 1:", part1(data))
console.timeEnd("Part 1 Time")

console.time("Part 2 Time")
console.log("Part 2:", part2(data))
console.timeEnd("Part 2 Time")