package advent2023

import kotlin.math.pow

private const val CARD = "Card"

private const val COLON_SEPARATOR = ":"

class Day04(private val input: List<String>) {

fun solvePart1(): Int {

return input.sumOf { card ->

val matchCount = findMatchCountForCard(card)

2.0.pow(matchCount - 1).toInt()

}

}

fun solvePart2(): Int {

val cardToTotalCount = mutableMapOf<Int, Int>()

val cardToMatchCount = input.map { card ->

val cardNumber = card.substringAfter(CARD)

.substringBefore(COLON_SEPARATOR)

.trim()

.toInt()

.also {

// init `cardToTotalCount` with each card occurring once

cardToTotalCount[it] = 1

}

cardNumber to findMatchCountForCard(card)

}

cardToMatchCount.forEach { (cardNumber, matchCount) ->

repeat(matchCount) {

cardToTotalCount[cardNumber + it + 1] =

checkNotNull(cardToTotalCount[cardNumber + it + 1]) + checkNotNull(cardToTotalCount[cardNumber])

}

}

return cardToTotalCount.map { it.value }.sum()

}

private fun findMatchCountForCard(cardInfo: String): Int {

val numbers = cardInfo.split(":").last().split("|")

val winningNumbers = numbers

.first()

.split(" ")

.filter { it.isNotEmpty() }

.map { it.trim() }

.map { it.toInt() }

val cardsInHand = numbers

.last()

.split(" ")

.filter { it.isNotEmpty() }

.map { it.trim() }

.map { it.toInt() }

var count = 0

cardsInHand.forEach { number ->

if (number in winningNumbers) {

count += 1

}

}

return count

}

}

fun main() {

val input = Resources.resourceAsListOfString("advent2023/day04.txt")

val day04 = Day04(input = input)

println("Part 1 Solution: ${day04.solvePart1()}")

println("Part 2 Solution: ${day04.solvePart2()}")

}