feat(aoc-2023): add day 6 part 1 and part 2

Author: markkovari

2023/src/main/scala/com/markkovari/adventofcode/day06.scala

@@ -1,5 +1,42 @@
 package com.markkovari.adventofcode.day06
 
-def part1(input: String): Long = 288
+// Oh boy, did I port this https://github.com/tlareg/advent-of-code/blob/master/src/2023/day06/index.ts ?
+// I sure did
 
-def part2(input: String): Long = 2
+type Race = (Long, Long)
+
+def part1(input: String): Long = {
+  // should not collect iterator to array, but I'm lazy, just like my algorithms
+  val lines = input.linesIterator.toArray
+  val times = lines(0).split("\\s+").drop(1).map(_.toInt)
+  val distances = lines(1).split("\\s+").drop(1).map(_.toInt)
+  val races = times.map(_.toLong).zip(distances.map(_.toLong))
+  solveForRaces(races)
+}
+
+def solveForRaces(races: Array[Race]): Long = {
+  races
+    .map((a, b) => getNumberOfWaysBeatingRecord(a, b))
+    .product
+}
+
+def getNumberOfWaysBeatingRecord(raceTime: Long, recordDistance: Long): Long = {
+  (0 until raceTime.toInt)
+    .map(holdTime => getDistance(holdTime, raceTime))
+    .count(distanceByHold => distanceByHold > recordDistance)
+}
+
+def getDistance(holdTime: Long, raceTime: Long): Long =
+  holdTime * (raceTime - holdTime)
+
+def part2(input: String): Long = {
+  val lines = input.linesIterator.toArray
+  val time = parseLineForPart2(lines(0))
+  val distance = parseLineForPart2(lines(1))
+  solveForRaces(Array[Race]((time, distance)))
+}
+
+def parseLineForPart2(line: String): Long = {
+  val num = line.split(":")(1).trim().split("\\s+").mkString
+  num.toLong
+}

2023/src/test/scala/com/markkovari/adventofcode/Day06Tests.scala

@@ -1,6 +1,6 @@
 package com.markkovari.adventofcode
 
-import com.markkovari.adventofcode.day06.part1
+import com.markkovari.adventofcode.day06.*
 import org.scalatest.funsuite.AnyFunSuite
 
 import scala.io.Source
@@ -11,4 +11,22 @@ class Day06Tests extends AnyFunSuite {
     assert(part1(source.mkString) === 288)
     source.close()
   }
+
+  test("Part1 solution") {
+    val source = io.Source.fromFile("./src/test/resources/6/values")
+    assert(part1(source.mkString) === 4403592)
+    source.close()
+  }
+
+  test("Part2 example") {
+    val source = io.Source.fromFile("./src/test/resources/6/example_1")
+    assert(part2(source.mkString) === 71503)
+    source.close()
+  }
+
+  test("Part2 solution") {
+    val source = io.Source.fromFile("./src/test/resources/6/values")
+    assert(part2(source.mkString) === 38017587)
+    source.close()
+  }
 }