Day01.kt

package adventofcode2023

import java.io.File

object Day01 {
    fun part1(inputs: List<String>) {
        println(inputs.sumOf { line ->
            val digits = line.filter { char -> char.isDigit() }
            digits.first().digitToInt() * 10 + digits.last().digitToInt()
        })
    }

    fun part2(inputs: List<String>) {
        val digits = setOf(
            Pair("one", '1'),
            Pair("two", '2'),
            Pair("three", '3'),
            Pair("four", '4'),
            Pair("five", '5'),
            Pair("six", '6'),
            Pair("seven", '7'),
            Pair("eight", '8'),
            Pair("nine", '9')
        )

        fun findDigit(line: String, indices: IntProgression = line.indices): Int {
            for (i in indices) {
                for (digit in digits) {
                    if ((line.length >= i + digit.first.length
                                && line.substring(i, i + digit.first.length) == digit.first)
                        || line[i] == digit.second
                    ) {
                        return digit.second.digitToInt()
                    }
                }
            }

            return 0
        }

        println(inputs.sumOf { line ->
            findDigit(line) * 10 + findDigit(line, line.indices.reversed())
        })
    }
}

fun main() {
    val inputs = File("resources/adventofcode2023/Day01.txt").readLines()
    Day01.part1(inputs)
    Day01.part2(inputs)
}