2022 Day 7 Scala

2022/day07.scala

@@ -0,0 +1,35 @@
+val fileSizePattern = raw"(\d+) ([\w.]+)".r
+val cdPattern = "\\$ cd ([\\/\\w.]+)".r  // raw string interpolation doesn't like \$
+val rootPattern = raw"\/(.*)".r
+
+def cd(cwd: String, to: String): String = to match
+	case rootPattern(absPath) => absPath  // Absolute path
+	case ".." => 
+		val i = cwd.lastIndexOf('/')
+		if i < 0 then cwd else cwd.substring(0, i)  // Up one subfolder
+	case _ => s"$cwd/$to"
+
+@main def main() =
+	val inputLines = scala.io.Source.fromFile("input/07").getLines
+
+	var cwd = ""  // We append the / at time of use
+	val folders = scala.collection.mutable.HashSet[String](cwd)
+	val fileSizes = scala.collection.mutable.HashMap[String, Int]()
+	for line <- inputLines do
+		line match
+			case cdPattern(dir) =>
+				cwd = cd(cwd, dir)
+				folders += cwd
+			case fileSizePattern(sizeStr, filename) =>
+				fileSizes += (s"$cwd/$filename" -> sizeStr.toInt)
+			case _ => {}  // "$ ls", "dir ..."
+	// Very inefficient way of calculating folder sizes, but cute enough
+	val folderSizes = folders.map(f => (f, fileSizes.filter((k,v) => k startsWith s"$f/").values.sum)).toMap
+
+	println(s"Part 1: ${folderSizes.values.filter(v => v <= 100_000).sum}")
+
+	val totalCapacity = 70_000_000
+	val desiredRemaining = 30_000_000
+	val currentRemaining = totalCapacity - folderSizes("")
+	val sizeToDelete = desiredRemaining - currentRemaining
+	println(s"Part 2: ${folderSizes.values.filter(v => v > sizeToDelete).min}")