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Day11.kt
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Day11.kt
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package day11
import com.github.keelar.exprk.Expressions
import common.InputRepo
import common.readSessionCookie
import common.solve
import util.split
import java.math.BigInteger
data class MonkeyTest(val divisor: Int, val positive: Int, val negative: Int)
data class Monkey(
val id: Int,
val items: MutableList<BigInteger>,
val operation: String,
val test: MonkeyTest
) {
var inspects = 0L
fun executeOperation(worryLevel: BigInteger): BigInteger {
inspects++
return Expressions()
.define("old", worryLevel.toBigDecimal())
.eval(operation)
.toBigInteger()
}
fun executeTest(worryLevel: BigInteger): Int {
return if (worryLevel % test.divisor.toBigInteger() == BigInteger.ZERO) {
test.positive
} else {
test.negative
}
}
}
fun main(args: Array<String>) {
val day = 11
val input = InputRepo(args.readSessionCookie()).get(day = day)
solve(day, input, ::solveDay11Part1, ::solveDay11Part2)
}
fun solveDay11Part1(input: List<String>): Long {
val monkeys = input.split({ it.isBlank() })
.map { convertToMonkey(it) }
println(monkeys)
repeat(20, action = {
for (monkey in monkeys) {
for (item in monkey.items) {
println("${monkey.id} inspects item with worry level ${item}")
val worry = monkey.executeOperation(item) / BigInteger.valueOf(3L)
val target = monkey.executeTest(worry)
println("throw to $target")
monkeys.first { it.id == target }.items.add(worry)
}
monkey.items.clear()
}
})
val mostActive = monkeys.sortedByDescending { it.inspects }
return mostActive[0].inspects * mostActive[1].inspects
}
fun convertToMonkey(monkeyDefinition: Collection<String>): Monkey {
val startingItemsPrefix = "Starting items:"
val opPrefix = "Operation:"
var id = 0
var list: MutableList<BigInteger> = emptyList<BigInteger>().toMutableList()
var operation = ""
var divisor = 0
var pos = 0
var neg = 0
// this is why I just should have used RegEx.
for (line in monkeyDefinition.map { it.trim() }) {
if (line.startsWith("Monkey")) {
id = line.removePrefix("Monkey")
.trim()
.removeSuffix(":")
.toInt()
}
if (line.startsWith(startingItemsPrefix)) {
list = line.removePrefix(startingItemsPrefix)
.trim()
.split(", ").map { BigInteger.valueOf(it.toLong()) }.toMutableList()
}
if (line.startsWith(opPrefix)) {
operation = line.removePrefix(opPrefix)
.trim()
.removePrefix("new =")
.trim()
}
if (line.startsWith("Test:")) {
divisor = line.removePrefix("Test: divisible by")
.trim()
.toInt()
}
if (line.startsWith("Test:")) {
divisor = line.removePrefix("Test: divisible by")
.trim()
.toInt()
}
if (line.startsWith("If true: throw to monkey ")) {
pos = line.removePrefix("If true: throw to monkey ")
.trim()
.toInt()
}
if (line.startsWith("If false: throw to monkey ")) {
neg = line.removePrefix("If false: throw to monkey ")
.trim()
.toInt()
}
}
return Monkey(id, list, operation, MonkeyTest(divisor, pos, neg))
}
fun solveDay11Part2(input: List<String>): Long {
val monkeys = input.split({ it.isBlank() })
.map { convertToMonkey(it) }
// gcd for all primes is just multiplication
val gcd = monkeys.map { it.test.divisor }.reduce { acc: Int, current: Int -> acc * current }
repeat(10000, action = {
for (monkey in monkeys) {
for (item in monkey.items) {
val worry = monkey.executeOperation(item) % gcd.toBigInteger()
val target = monkey.executeTest(worry)
monkeys.first { it.id == target }.items.add(worry)
}
monkey.items.clear()
}
})
val mostActive = monkeys.sortedByDescending { it.inspects }
mostActive.forEach { println("${it.id}: ${it.inspects}") }
return mostActive[0].inspects * mostActive[1].inspects
}