Day08Matchsticks.kt

package adventofcode.year2015

import adventofcode.Puzzle
import adventofcode.PuzzleInput

class Day08Matchsticks(customInput: PuzzleInput? = null) : Puzzle(customInput) {
    override fun partOne() = input
        .lines()
        .sumOf { string ->
            val decodedString = string
                .substring(1 until string.length - 1)
                .replace("""\\x([0-9a-f]{2})""".toRegex()) { it.destructured.component1().toInt(16).toChar().toString() }
                .replace("""\\""", """\""")
                .replace("\\\"", "\"")

            string.length - decodedString.length
        }

    override fun partTwo() = input
        .lines()
        .sumOf { ("\"" + it.replace("\\", "\\\\").replace("\"", "\\\"") + "\"").length - it.length }
}