Day 10, a day late

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

@@ -7,10 +7,10 @@ import java.util.stream.Stream
 
 fun lines(resourceFile: String): Stream<String> {
 
-    val uri = Paths.get(Utils::class.java.getResource(resourceFile).toURI())
-    val env = mapOf(Pair("create", "true"))
-    FileSystems.newFileSystem(uri, env)
-    return Files.lines(uri)
+    val uri = Utils::class.java.getResource(resourceFile).toURI()
+//    val env = mapOf(Pair("create", "true"))
+//    FileSystems.newFileSystem(uri, env)
+    return Files.lines(Paths.get(uri))
 }
 
 fun line(resourceFile: String): String {

src/main/kotlin/com/basdado/adventofcode/day10/Day10.kt

@@ -1,33 +1,121 @@
-const val DAY10_INPUT_PATH = "/day/10/input.txt"
+package com.basdado.adventofcode.day10
 
-import com.basdado.adventofcode.lines;
-import java.util.stream.Collectors;
+import com.basdado.adventofcode.lines
+import java.util.stream.Collectors
+import kotlin.math.PI
+import kotlin.math.abs
+import kotlin.math.atan2
+import kotlin.math.min
+
+const val DAY10_INPUT_PATH = "/day/10/input.txt"
 
 fun main() {
 
+//    val circle = listOf(
+//        Day10.Vector2i(0, 1),
+//        Day10.Vector2i(1, 1),
+//        Day10.Vector2i(1, 0),
+//        Day10.Vector2i(0, -1),
+//        Day10.Vector2i(-1, -1),
+//        Day10.Vector2i(-1, 0),
+//        Day10.Vector2i(-1, 1)
+//        )
+//
+//    circle.map {
+//        - (it.angle() + 0.5 * PI)
+//    }.map { if (it < 0) it + 2 * PI else it }.forEach(::println)
+
+//    println(Day10.Vector2i(5, 2).angle())
+
     Day10.puzzle1()
-    // Day10.puzzle2()
+    Day10.puzzle2()
 }
 
 object Day10 {
 
     fun puzzle1() {
-        println("Hello world!")
-        val rawData = lines(DAY10_INPUT_PATH).collect(Collectors.toList())
-        val asteroids = 
-        (0..rawData.size).forEach { y ->
-            (0..rawData[y].length).forEach { x ->
-                if (rawData[y][x] == '#') {
-                    
-                }
-            }
-        }
+        val asteroids = loadAsteroids()
+        println(optimalAsteroidsPerDirection(asteroids).second.size)
 
     }
 
+    fun puzzle2() {
+        val asteroids = loadAsteroids()
+        val optimalAsteroid = optimalAsteroidsPerDirection(asteroids)
+//        val optimalAsteroid = Pair(Vector2i(8, 3), asteroidsPerDirection(Vector2i(8, 3), asteroids))
+//        println(optimalAsteroid.first)
+//        optimalAsteroid.second.keys.forEach {
+//            var angle = (it.angle() + 0.5 * PI);
+//            angle = if (angle < 0) 2*PI + angle else angle
+//            println("(${it.x}, ${it.y}) = $angle")
+//        }
+        val sortedAsteroidLists = optimalAsteroid.second
+            .entries
+            .sortedBy { val angle = (it.key.angle() + 0.5 * PI); if (angle < 0) 2*PI + angle else angle }
+            .map { it.value.sortedBy( Vector2i::manhattan ) }
+        // And now we're gonna keep taking one of each list until we reach number 200
+        var listIndex = 0
+        var itemIndexPerList = IntArray(sortedAsteroidLists.size)
+        var i = 0
+        var curItem: Vector2i? = null
+        while (i < 200) {
+            val list = sortedAsteroidLists[listIndex]
+            if (itemIndexPerList[listIndex] < list.size) {
+                curItem = list[itemIndexPerList[listIndex]]
+//                println(optimalAsteroid.first + curItem)
+                itemIndexPerList[listIndex]++
+                i++
+            }
+            listIndex++
+        }
+        val asteroid200 = optimalAsteroid.first + curItem!!
+        println(asteroid200.x * 100 + asteroid200.y)
+    }
+
+    private fun optimalAsteroidsPerDirection(asteroids: List<Vector2i>): Pair<Vector2i, Map<Vector2i, List<Vector2i>>> {
+        return asteroids.map { Pair(it, asteroidsPerDirection(it, asteroids)) }.maxBy { it.second.size }!!
+    }
+
+    private fun asteroidsPerDirection(asteroid: Vector2i, asteroids: List<Vector2i>): Map<Vector2i, List<Vector2i>> {
+        return asteroids
+                .filter { it != asteroid }
+                .map { it - asteroid }
+                .groupBy { it.normalize() }
+    }
+
+    private fun loadAsteroids(): List<Vector2i> {
+        val rawData = lines(DAY10_INPUT_PATH).collect(Collectors.toList())
+        return (0 until rawData.size).flatMap { y ->
+            (rawData[y].indices)
+                .filter { x -> rawData[y][x] == '#' }
+                .map { x -> Vector2i(x, y) }
+        }
+    }
+
     data class Vector2i(val x: Int, val y: Int) {
+
         fun normalize(): Vector2i {
-            
+            return this / gcd(x, y)
         }
+
+        fun angle() = atan2(y.toDouble(), x.toDouble())
+        fun manhattan() = abs(x) + abs(y)
+
+        operator fun div(d: Int) = Vector2i(x / d, y / d)
+        operator fun minus(n: Int) = Vector2i(x - n, y - n)
+        operator fun minus(v: Vector2i) = Vector2i(x - v.x, y - v.y)
+        operator fun plus(n: Int) = Vector2i(x + n, y + n)
+        operator fun plus(v: Vector2i) = Vector2i(x + v.x, y + v.y)
+    }
+
+    val ORIGIN = Vector2i(0, 0)
+
+    fun gcd(n1: Int, n2: Int) = when {
+        n1 == 0 && n2 == 0 -> 1 // Actually undefined/any number, but whatever
+        n1 == 0 -> abs(n2)
+        n2 == 0 -> abs(n1)
+        else -> (1..(min(abs(n1), abs(n2))))
+            .filter { n1 % it == 0 && n2 % it == 0 }
+            .max() ?: 1
     }
 }

src/main/resources/day/10/ex0.txt

@@ -0,0 +1,5 @@
+.#....#####...#..
+##...##.#####..##
+##...#...#.#####.
+..#.....X...###..
+..#.#.....#....##

src/main/resources/day/10/ex1.txt

@@ -0,0 +1,10 @@
+......#.#.
+#..#.#....
+..#######.
+.#.#.###..
+.#..#.....
+..#....#.#
+#..#....#.
+.##.#..###
+##...#..#.
+.#....####

src/main/resources/day/10/ex2.txt

@@ -0,0 +1,10 @@
+#.#...#.#.
+.###....#.
+.#....#...
+##.#.#.#.#
+....#.#.#.
+.##..###.#
+..#...##..
+..##....##
+......#...
+.####.###.

src/main/resources/day/10/ex3.txt

@@ -0,0 +1,10 @@
+.#..#..###
+####.###.#
+....###.#.
+..###.##.#
+##.##.#.#.
+....###..#
+..#.#..#.#
+#..#.#.###
+.##...##.#
+.....#.#..

src/main/resources/day/10/ex4.txt

@@ -0,0 +1,20 @@
+.#..##.###...#######
+##.############..##.
+.#.######.########.#
+.###.#######.####.#.
+#####.##.#.##.###.##
+..#####..#.#########
+####################
+#.####....###.#.#.##
+##.#################
+#####.##.###..####..
+..######..##.#######
+####.##.####...##..#
+.#####..#.######.###
+##...#.##########...
+#.##########.#######
+.####.#.###.###.#.##
+....##.##.###..#####
+.#.#.###########.###
+#.#.#.#####.####.###
+###.##.####.##.#..##