Solve 2025 day 2 part 1

Author: sim642

src/main/resources/eu/sim642/adventofcode2025/day2.txt

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+9191896883-9191940271,457499-518693,4952-6512,960-1219,882220-1039699,2694-3465,3818-4790,166124487-166225167,759713819-759869448,4821434-4881387,7271-9983,1182154-1266413,810784-881078,802-958,1288-1491,45169-59445,25035-29864,379542-433637,287-398,75872077-75913335,653953-689335,168872-217692,91-113,475-590,592-770,310876-346156,2214325-2229214,85977-112721,51466993-51620441,8838997-8982991,534003-610353,32397-42770,17-27,68666227-68701396,1826294188-1826476065,1649-2195,141065204-141208529,7437352-7611438,10216-13989,33-44,1-16,49-74,60646-73921,701379-808878

src/main/scala/eu/sim642/adventofcode2025/Day2.scala

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+package eu.sim642.adventofcode2025
+
+import eu.sim642.adventofcode2016.Day20.Interval
+
+object Day2 {
+
+  type Range = Interval
+
+  val invalidIds: LazyList[Long] = LazyList.from(1).map(i =>
+    val len = i.toString.length // TODO: already have a (better) way to get number of digits?
+    i * (Math.powExact(10L, len) + 1)
+  )
+
+  def sumInvalidIds(ranges: Seq[Range]): Long = { // TODO: Long?
+    val max = ranges.map(_.max).max
+    invalidIds
+      .takeWhile(_ <= max)
+      .filter(id =>
+        ranges.exists(_.contains(id))
+      )
+      .sum
+  }
+
+  def parseRange(s: String): Range = s match {
+    case s"$i-$j" => Interval(i.toLong, j.toLong)
+  }
+
+  def parseRanges(input: String): Seq[Interval] = input.split(",").toSeq.map(parseRange)
+
+  lazy val input: String = scala.io.Source.fromInputStream(getClass.getResourceAsStream("day2.txt")).mkString.trim
+
+  def main(args: Array[String]): Unit = {
+    println(sumInvalidIds(parseRanges(input)))
+  }
+}

src/test/scala/eu/sim642/adventofcode2025/Day2Test.scala

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+package eu.sim642.adventofcode2025
+
+import Day2._
+import org.scalatest.funsuite.AnyFunSuite
+
+class Day2Test extends AnyFunSuite {
+
+  val exampleInput =
+    """11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124"""
+
+  test("Part 1 examples") {
+    assert(sumInvalidIds(parseRanges(exampleInput)) == 1227775554)
+  }
+
+  test("Part 1 input answer") {
+    assert(sumInvalidIds(parseRanges(input)) == 5398419778L)
+  }
+}