Solution 2018-03 (No Matter How You Slice It)

Author: rhaendel

src/main/kotlin/de/ronny_h/aoc/year2018/day03/NoMatterHowYouSliceIt.kt

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+package de.ronny_h.aoc.year2018.day03
+
+import de.ronny_h.aoc.AdventOfCode
+import de.ronny_h.aoc.extensions.grids.Coordinates
+
+fun main() = NoMatterHowYouSliceIt().run(107820, 661)
+
+class NoMatterHowYouSliceIt : AdventOfCode<Int>(2018, 3) {
+    override fun part1(input: List<String>): Int = ClaimedAreas(input).numberOfOverlaps()
+    override fun part2(input: List<String>): Int = ClaimedAreas(input).findTheOneThatDoesntOverlap().id
+}
+
+data class Claim(val id: Int, val x: Int, val y: Int, val width: Int, val height: Int)
+
+private val claimPattern = """#(\d+) @ (\d+),(\d+): (\d+)x(\d+)""".toPattern()
+
+fun List<String>.parseClaims() = map {
+    val matcher = claimPattern.matcher(it)
+    matcher.find()
+    check(matcher.groupCount() == 5)
+    Claim(
+        id = matcher.group(1).toInt(),
+        x = matcher.group(2).toInt(),
+        y = matcher.group(3).toInt(),
+        width = matcher.group(4).toInt(),
+        height = matcher.group(5).toInt(),
+    )
+}
+
+class ClaimedAreas(input: List<String>) {
+    private val claims = input.parseClaims()
+    private val claimedAreas = mutableMapOf<Coordinates, Int>().withDefault { 0 }
+
+    init {
+        claims.forEach {
+            for (x in it.x..<it.x + it.width) {
+                for (y in it.y..<it.y + it.height) {
+                    claimedAreas[Coordinates(y, x)] = claimedAreas.getValue(Coordinates(y, x)) + 1
+                }
+            }
+        }
+    }
+
+    fun numberOfOverlaps() = claimedAreas.values.count { it > 1 }
+
+    fun findTheOneThatDoesntOverlap(): Claim = claims
+        .filter {
+            for (x in it.x..<it.x + it.width) {
+                for (y in it.y..<it.y + it.height) {
+                    if (claimedAreas.getValue(Coordinates(y, x)) > 1) return@filter false
+                }
+            }
+            true
+        }
+        .single()
+}

src/test/kotlin/de/ronny_h/aoc/year2018/day03/NoMatterHowYouSliceItTest.kt

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+package de.ronny_h.aoc.year2018.day03
+
+import de.ronny_h.aoc.extensions.asList
+import io.kotest.core.spec.style.StringSpec
+import io.kotest.matchers.shouldBe
+
+class NoMatterHowYouSliceItTest : StringSpec({
+
+    val input = """
+        #1 @ 1,3: 4x4
+        #2 @ 3,1: 4x4
+        #3 @ 5,5: 2x2
+    """.asList()
+
+    "input can be parsed" {
+        input.parseClaims() shouldBe listOf(
+            Claim(1, 1, 3, 4, 4),
+            Claim(2, 3, 1, 4, 4),
+            Claim(3, 5, 5, 2, 2),
+        )
+    }
+
+    "part 1: the number of square inches of fabric within two or more claims" {
+        NoMatterHowYouSliceIt().part1(input) shouldBe 4
+    }
+
+    "part 2: the ID of the claim that doesn't overlap" {
+        NoMatterHowYouSliceIt().part2(input) shouldBe 3
+    }
+})