Add Day8

src/main/kotlin/Day08.kt

@@ -0,0 +1,51 @@
+import kotlin.math.max
+import utils.AoCDay
+import utils.Vec2D
+
+class Day08 : AoCDay() {
+    val map = mutableMapOf<Char, List<Vec2D>>()
+
+    init {
+        for (y in input.indices) {
+            for (x in input[0].indices) {
+                val char = input[y][x]
+                if (char == '.') continue
+                if (char !in map) map[char] = mutableListOf()
+                map[char] = map[char]!! + Vec2D(x, y)
+            }
+        }
+    }
+
+    override fun part1(): Any {
+        return solve()
+    }
+
+    override fun part2(): Any {
+        return solve(true)
+    }
+
+    private fun solve(partB: Boolean = false): Int {
+        val antiNodes = mutableSetOf<Vec2D>()
+        val maxSize = if (partB) max(input.size, input[0].length) else 1
+
+        for ((_, positions) in map) {
+            for (posA in positions) {
+                for (posB in positions) {
+                    if (posA == posB) continue
+
+                    repeat(maxSize + 1) { i ->
+                        if (!partB && i == 0) return@repeat
+                        antiNodes += posA + (posA - posB) * i
+                        antiNodes += posB + (posB - posA) * i
+                    }
+
+                }
+            }
+        }
+        return antiNodes.filter { it.y in input.indices && it.x in input[0].indices }.size
+    }
+}
+
+fun main() {
+    Day08().execute()
+}