Day 3

src/main/kotlin/com/basdado/adventofcode/Day3.kt

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+package com.basdado.adventofcode
+
+import java.util.stream.Collectors
+import java.util.stream.Stream
+import java.util.stream.StreamSupport
+
+fun main() {
+
+    val day = Day3()
+    day.puzzle1()
+    day.puzzle2()
+}
+
+class Day3 {
+
+    fun puzzle1() {
+        val grid = FabricGrid()
+
+        lines("/day/3/input.txt")
+            .forEach { grid.mark(it) }
+
+        println(
+            grid.stream()
+                .filter { it.size > 1}
+                .collect(Collectors.counting())
+        )
+    }
+
+    fun puzzle2() {
+
+        val grid = FabricGrid()
+
+        lines("/day/3/input.txt")
+            .forEach { grid.mark(it) }
+
+        val potentials = grid.stream().flatMap { it.stream() }.distinct().collect(Collectors.toSet())
+
+        grid.stream()
+            .filter{ it.size > 1 }
+            .flatMap { it.stream() }
+            .distinct()
+            .forEach { potentials.remove(it) }
+
+        println(potentials)
+    }
+}
+
+class FabricGrid: Iterable<List<Int>> {
+
+    private val grid = Array<MutableList<Int>>(1000 * 1000) { mutableListOf() }
+
+    fun getIdsAt(x: Int, y: Int): List<Int> = grid[x + y * 1000]
+    fun addId(x: Int, y: Int, id: Int) = grid[x + y * 1000].add(id)
+
+    override fun iterator(): Iterator<List<Int>> = grid.iterator()
+    fun stream(): Stream<List<Int>> = StreamSupport.stream(spliterator(), false)
+
+    fun mark(fabricPieceDefinition: String) {
+
+        if (fabricPieceDefinition.isEmpty()) {
+            return
+        }
+
+        val id = fabricPieceDefinition.substring(1, fabricPieceDefinition.indexOf('@')).trim().toInt()
+        val x = fabricPieceDefinition.substring(fabricPieceDefinition.indexOf('@') + 1, fabricPieceDefinition.indexOf(',')).trim().toInt()
+        val y = fabricPieceDefinition.substring(fabricPieceDefinition.indexOf(',') + 1, fabricPieceDefinition.indexOf(':')).trim().toInt()
+        val width = fabricPieceDefinition.substring(fabricPieceDefinition.indexOf(':') + 1, fabricPieceDefinition.indexOf('x')).trim().toInt()
+        val height = fabricPieceDefinition.substring(fabricPieceDefinition.indexOf('x') + 1).trim().toInt()
+
+        mark(id, x, y, width, height)
+    }
+
+    fun mark(id: Int, x: Int, y: Int, width: Int, height: Int) {
+
+        for (j in y until (y + height)) {
+            for (i in x until (x + width)) {
+                addId(i, j, id)
+            }
+        }
+    }
+}

src/main/kotlin/com/basdado/adventofcode/Utils.kt

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+package com.basdado.adventofcode
+
+import java.nio.file.Files
+import java.nio.file.Paths
+import java.util.stream.Stream
+
+fun lines(resourceFile: String): Stream<String> {
+    return Files.lines(Paths.get(Utils::class.java.getResource(resourceFile).toURI()))
+}
+
+class Utils;