2018 day 2

aoc/src/main/scala/aoc/package.scala

@@ -30,4 +30,12 @@ package object aoc {
     go(as, Set.empty)
   }
 
+  def levenshtein(a: String, b: String): Int =
+    ((0 to b.length).toList /: a)(
+      (prev, x) =>
+        (prev zip prev.tail zip b).scanLeft(prev.head + 1) {
+          case (h, ((d, v), y)) => Math.min(Math.min(h + 1, v + 1), d + (if (x == y) 0 else 1))
+      }
+    ).last
+
 }

aoc/src/main/scala/aoc/y2018/Day02.scala

@@ -0,0 +1,22 @@
+package aoc.y2018
+
+import aoc._
+
+object Day02 extends Day {
+
+  override def part1(input: String): String = {
+    val lines = input.lines.toList
+    val groups = lines.map(_.groupBy(identity))
+    val twos = groups.count(_.values.exists(_.length == 2))
+    val threes = groups.count(_.values.exists(_.length == 3))
+    (twos * threes).toString
+  }
+
+  override def part2(input: String): String = {
+    val lines = input.lines.toList
+    val distanceMap = lines.flatMap(s => lines.map(c => ((s, c), levenshtein(s, c)))).toMap
+    val ((s, c), _) = distanceMap.filter {case (_, d) => d > 0 }.minBy { case (_, d) => d }
+    s.intersect(c).mkString
+  }
+
+}

aoc/src/main/scala/aoc/y2018/package.scala

@@ -3,7 +3,8 @@ package aoc
 package object y2018 extends Year {
 
   override def days: Map[String, Day] = Map(
-    "1" -> Day01
+    "1" -> Day01,
+    "2" -> Day02
   )
 
 }