[day2] solution + refactoring of day 1/main

README.md

@@ -15,11 +15,9 @@ sbt '++ 3.0.0-M1 publishLocal'
 To run the code for a day:
 
 ```
-sbt "run <input_dir> <day> <part>"
+sbt "run <input_dir> <day>"
 ```
-where
-- `<input_dir>` is the path to a folder with AOC inputs named "day1.txt", "day2.txt", ...  
-	Can be downloaded e.g. using [cargo-aoc](https://github.com/gobanos/cargo-aoc)
-- `<day>` is the day to run
-- `<part>` is either 1 or 2. Defaults to 1 if not given
-1
+where `<input_dir>` is the path to a folder with AOC inputs named "day1.txt", "day2.txt", ...
+and `<day>` is the day to run.
+
+Inputs can be downloaded e.g. using [cargo-aoc](https://github.com/gobanos/cargo-aoc) or of course manually.

src/main/scala/Day1.scala

-def day1_1(input: List[Int]): Int = 
-  input.groupWithSum(2020, groupSize = 2).product
-
-def day1_2(input: List[Int]): Int = 
-  input.groupWithSum(2020, groupSize = 3).product
+def day1(input: List[Int]): String =
+  List(2, 3).map(groupSize => input.groupWithSum(2020, groupSize).product)
+    .mkString("\n")
 
 extension (input: List[Int]) def groupWithSum(sum: Int, groupSize: Int = 2): List[Int] =
   input.combinations(groupSize).filter(_.sum == sum).next

src/main/scala/Day2.scala

+def day2(passwords: List[String]): String =
+  List(
+    passwords.count(validAmount),
+    passwords.count(validPositions)
+  ).mkString("\n")
+  
+
+// part 1, password must contain given amount of character
+def validAmount(passLine: String): Boolean =
+  val (min, max, char, pass) = parse(passLine)
+  (min to max) contains pass.count(_ == char)
+
+// part 2, password must contain character at exactly one of the given positions
+def validPositions(passLine: String): Boolean =
+  val (a, b, char, pass) = parse(passLine)
+  pass(a-1) == char ^ pass(b-1) == char
+
+def parse(passLine: String): (Int, Int, Char, String) =
+  val s"$min-$max $char:$pass" = passLine
+  (min.toInt, max.toInt, char(0), pass)

src/main/scala/Main.scala

-@main def runDay(inputDir: String, day: Int, part: Int = 1): Unit =
+@main def runDay(inputDir: String, day: Int): Unit =
   val s = scala.io.Source.fromFile(s"${inputDir}/day${day}.txt").getLines
-  val out = (day, part) match {
-    case (1, 1) => day1_1(s.map(_.toInt).toList).toString
-    case (1, 2) => day1_2(s.map(_.toInt).toList).toString
+  val out = day match {
+    case 1 => day1(s.map(_.toInt).toList)
+    case 2 => day2(s.toList)
   }
   println(out)