Prepare for other years

2020/src/main/kotlin/Day10.kt

@@ -0,0 +1,44 @@
+package be.vandewalleh.aoc.days
+
+import be.vandewalleh.aoc.utils.input.Day
+import be.vandewalleh.aoc.utils.input.Input
+import be.vandewalleh.aoc.utils.input.Lines
+import org.eclipse.collections.api.list.primitive.MutableIntList
+import org.eclipse.collections.impl.factory.primitive.IntLists
+import org.eclipse.collections.impl.factory.primitive.IntLongMaps
+
+@Day(10)
+class Day10(@Lines val input: Input<IntArray>) {
+
+    fun part1(): Int {
+        val sorted = IntLists.mutable.of(0, *input.value).apply {
+            sortThis()
+            add(last + 3)
+        }.toArray().toList()
+
+        var ones = 0
+        var threes = 0
+
+        sorted.zipWithNext().forEach { (a, b) ->
+            if (a + 1 == b) ones++
+            else if (a + 3 == b) threes++
+        }
+
+        return ones * threes
+    }
+
+    fun part2(): Long {
+        val sorted: MutableIntList = IntLists.mutable.of(*input.value).apply { sortThis() }
+
+        val map = IntLongMaps.mutable.empty().apply {
+            put(0, 1L)
+        }
+
+        sorted.forEach { i ->
+            map.put(i, map.get(i - 1) + map.get(i - 2) + map.get(i - 3))
+        }
+
+        return map.get(sorted.last)
+    }
+
+}