2022-13.js

const fs = require("fs")

const readData = () => {
  const data = fs
    .readFileSync("./input2022-13.txt", "utf-8")
    .split(/\r?\n\r?\n/)
    .map(line => line.split(/\r?\n/).map(part => JSON.parse(part)))

  return data
}

const main = () => {
  const pairs = readData()

  const compare = ([left, right]) => {
    if ([left, right].every(Number.isInteger)) {
      if (left < right) return true
      if (left > right) return false
      return
    }

    if ([left, right].every(Array.isArray)) {
      for (let i = 0; i < Math.min(left.length, right.length); i++) {
        const res = compare([left[i], right[i]])
        if (res != null) return res
      }

      return compare([left.length, right.length])
    }

    return compare([[left].flat(), [right].flat()])
  }

  const dividers = [[[2]], [[6]]]

  const res = [...pairs.flat(), ...dividers]
    .sort((left, right) => compare([right, left]) - compare([left, right]))
    .reduce(
      (acc, el, index) => (dividers.includes(el) ? acc * (index + 1) : acc),
      1
    )

  console.log(res)
}

main()