Day 5: Print Queue

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FAQ

  • @[email protected]
    5•7 days ago

    Kotlin

    Took me a while to figure out how to sort according to the rules. 🤯

    fun part1(input: String): Int {
    val (rules, listOfNumbers) = parse(input)
    return listOfNumbers
        .filter { numbers -> numbers == sort(numbers, rules) }
        .sumOf { numbers -> numbers[numbers.size / 2] }
}

fun part2(input: String): Int {
    val (rules, listOfNumbers) = parse(input)
    return listOfNumbers
        .filterNot { numbers -> numbers == sort(numbers, rules) }
        .map { numbers -> sort(numbers, rules) }
        .sumOf { numbers -> numbers[numbers.size / 2] }
}

private fun sort(numbers: List<Int>, rules: List<Pair<Int, Int>>): List<Int> {
    return numbers.sortedWith { a, b -> if (rules.contains(a to b)) -1 else 1 }
}

private fun parse(input: String): Pair<List<Pair<Int, Int>>, List<List<Int>>> {
    val (rulesSection, numbersSection) = input.split("\n\n")
    val rules = rulesSection.lines()
        .mapNotNull { line -> """(\d{2})\|(\d{2})""".toRegex().matchEntire(line) }
        .map { match -> match.groups[1]?.value?.toInt()!! to match.groups[2]?.value?.toInt()!! }
    val numbers = numbersSection.lines().map { line -> line.split(',').map { it.toInt() } }
    return rules to numbers
}
      • @[email protected]
        1•7 days ago

        I guess adding type aliases and removing the regex from parser makes it a bit more readable.

        typealias Rule = Pair<Int, Int>
typealias PageNumbers = List<Int>

fun part1(input: String): Int {
    val (rules, listOfNumbers) = parse(input)
    return listOfNumbers
        .filter { numbers -> numbers == sort(numbers, rules) }
        .sumOf { numbers -> numbers[numbers.size / 2] }
}

fun part2(input: String): Int {
    val (rules, listOfNumbers) = parse(input)
    return listOfNumbers
        .filterNot { numbers -> numbers == sort(numbers, rules) }
        .map { numbers -> sort(numbers, rules) }
        .sumOf { numbers -> numbers[numbers.size / 2] }
}

private fun sort(numbers: PageNumbers, rules: List<Rule>): PageNumbers {
    return numbers.sortedWith { a, b -> if (rules.contains(a to b)) -1 else 1 }
}

private fun parse(input: String): Pair<List<Rule>, List<PageNumbers>> {
    val (rulesSection, numbersSection) = input.split("\n\n")
    val rules = rulesSection.lines()
        .mapNotNull { line ->
            val parts = line.split('|').map { it.toInt() }
            if (parts.size >= 2) parts[0] to parts[1] else null
        }
    val numbers = numbersSection.lines()
        .map { line -> line.split(',').map { it.toInt() } }
    return rules to numbers
}