Day 4

aoc/src/Day4.scala

@@ -0,0 +1,29 @@
+import scala.io.Source
+
+object Day4 extends App:
+
+  val input = Source
+    .fromURL(getClass.getResource("day4Input.txt"))
+    .mkString
+    .split('\n')
+    .toList
+
+  def parsePair(string: String): (List[Int], List[Int]) =
+    string.split(',').map(parseRange) match
+      case Array(elf1, elf2) => (elf1, elf2)
+
+  def parseRange(string: String): List[Int] =
+    string.split('-').map(_.toInt) match
+      case Array(from, to) => List.range(from, to + 1)
+
+  val part1 = input
+    .map(parsePair)
+    .count(pair => pair._1.containsSlice(pair._2) || pair._2.containsSlice(pair._1))
+
+  println(s"Part 1: $part1")
+
+  val part2 = input
+    .map(parsePair)
+    .count(pair => pair._1.intersect(pair._2).size > 0)
+
+  println(s"Part 2: $part2")