Day 5: Print Queue

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FAQ

  • proved_unglue@programming.dev
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    10 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
    }