Day 1

Day1.scala

@@ -0,0 +1,45 @@
+// Part 1
+
+def literalDigits(s: String) =
+  s.toSeq.filter(_.isDigit).map(v => (v - '0').toInt)
+
+def getValue(toDigits: String => Seq[Int])(s: String): Int =
+  val digits = toDigits(s)
+  digits.head * 10 + digits.last
+
+def iterate[T](get: => T | Null) = new scala.collection.IterableOnce[T]:
+  override def iterator = new Iterator[T]:
+    var item: Option[T | Null] = None
+    override def hasNext: Boolean =
+      if item.isEmpty then item = Some(get)
+      item.get != null
+    override def next(): T =
+      val r = item.get.nn
+      item = None
+      r
+
+def getSum(toDigits: String => Seq[Int]) =
+  val values =
+    Seq.from(iterate(scala.io.StdIn.readLine())).map(getValue(toDigits))
+  println(values.sum)
+
+// Part 2
+
+val englishDigits =
+  Seq("one", "two", "three", "four", "five", "six", "seven", "eight", "nine")
+
+def literalOrEnglishDigits(s: String) =
+  @scala.annotation.tailrec
+  def loop(idx: Int, accum: Seq[Int]): Seq[Int] =
+    if idx < 0 then accum
+    else if s(idx).isDigit then loop(idx - 1, (s(idx) - '0').toInt +: accum)
+    else
+      val toMatch = s.slice(idx, idx + 5 /* enough to match english */ )
+      val digit = englishDigits.indexWhere(toMatch.startsWith _)
+      val nAccum = if digit == -1 then accum else (digit + 1) +: accum
+      loop(idx - 1, nAccum)
+  loop(s.length() - 1, Seq.empty)
+
+@main def Run(part: Int) = part match
+  case 1 => getSum(literalDigits)
+  case 2 => getSum(literalOrEnglishDigits)