AoC 2024 day 7

// Advent of Code 2024 - Day 7
const fs = require("fs")

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

const parseInput = (rawInput) =>
    rawInput.split(/\r?\n/).map((line) => {
        const [testValue, numbers] = line.split(":")
        return {
            testValue: Number(testValue),
            numbers: numbers.trim().split(" ").map(Number)
        }
    })

const evaluateExpression = (numbers, operators) =>
    operators.reduce((result, op, i) => {
        const next = numbers[i + 1]
        if (op === "+") return result + next
        if (op === "*") return result * next
        if (op === "||") return Number(result + "" + next)
        return result
    }, numbers[0])

const generateOperators = (length, allowConcat) => {
    const operators = allowConcat ? ["+", "*", "||"] : ["+", "*"]
    return length === 0
        ? [[]]
        : generateOperators(length - 1, allowConcat).flatMap((combo) => operators.map((op) => [op, ...combo]))
}

const solve = (data, allowConcat) => {
    const operatorCombosCache = new Map()
    return data.reduce((total, { testValue, numbers }) => {
        const key = numbers.length - 1
        if (!operatorCombosCache.has(key)) {
            operatorCombosCache.set(key, generateOperators(key, allowConcat))
        }

        const operatorCombos = operatorCombosCache.get(key)
        const isSolvable = operatorCombos.some((operators) => evaluateExpression(numbers, operators) === testValue)

        return total + (isSolvable ? testValue : 0)
    }, 0)
}

const data = parseInput(input)

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

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