Solution 2018-14 (Chocolate Charts)

Author: rhaendel

src/main/kotlin/de/ronny_h/aoc/year2018/day14/ChocolateCharts.kt

@@ -0,0 +1,48 @@
+package de.ronny_h.aoc.year2018.day14
+
+import de.ronny_h.aoc.AdventOfCode
+
+fun main() = ChocolateCharts().run("5992684592", "20181148")
+
+class ChocolateCharts : AdventOfCode<String>(2018, 14) {
+    override fun part1(input: List<String>): String {
+        val numberOfRecipes = input.single().toInt()
+        return ScoreBoard()
+            .createNewRecipesUntil { it.size == numberOfRecipes + 10 }
+            .substring(numberOfRecipes, numberOfRecipes + 10)
+    }
+
+    override fun part2(input: List<String>): String {
+        val inputString = input.single()
+        val puzzleInput = inputString.toList().map(Char::digitToInt)
+        return ScoreBoard()
+            .createNewRecipesUntil { it.endsWithSubList(puzzleInput) }
+            .substringBefore(inputString).length.toString()
+    }
+}
+
+private fun List<Int>.endsWithSubList(sublist: List<Int>): Boolean {
+    if (size < sublist.size) return false
+    return subList(size - sublist.size, size) == sublist
+}
+
+private class ScoreBoard {
+    private val scores = mutableListOf(3, 7)
+
+    fun createNewRecipesUntil(stopCondition: (List<Int>) -> Boolean): String {
+        var indexOne = 0
+        var indexTwo = 1
+        while (true) {
+            val scoreOne = scores[indexOne]
+            val scoreTwo = scores[indexTwo]
+            "${scoreOne + scoreTwo}".forEach {
+                scores.add(it.digitToInt())
+                if (stopCondition(scores)) {
+                    return scores.joinToString("")
+                }
+            }
+            indexOne = (indexOne + 1 + scoreOne) % scores.size
+            indexTwo = (indexTwo + 1 + scoreTwo) % scores.size
+        }
+    }
+}

src/test/kotlin/de/ronny_h/aoc/year2018/day14/ChocolateChartsTest.kt

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+package de.ronny_h.aoc.year2018.day14
+
+import io.kotest.core.spec.style.StringSpec
+import io.kotest.data.forAll
+import io.kotest.data.row
+import io.kotest.matchers.shouldBe
+
+class ChocolateChartsTest : StringSpec({
+
+    "part 1: the scores of the next 10 recipes after" {
+        forAll(
+            row(5, "0124515891"),
+            row(9, "5158916779"),
+            row(18, "9251071085"),
+            row(2018, "5941429882"),
+        ) { after, scores ->
+            ChocolateCharts().part1(listOf("$after")) shouldBe scores
+        }
+    }
+
+    "part 2: the number of recipes appear on the scoreboard to the left of the score sequence in the puzzle input" {
+        forAll(
+            row("01245", "5"),
+            row("51589", "9"),
+            row("92510", "18"),
+            row("59414", "2018"),
+        ) { puzzleInput, numberOfRecipesBefore ->
+            ChocolateCharts().part2(listOf(puzzleInput)) shouldBe numberOfRecipesBefore
+        }
+    }
+})