Solve the day 25 puzzle

Author: rvprasad

day25/README.md

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+Execute this code via `scala day25.scala -- <filename>`.
+
+### Observations
+

day25/day25.scala

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+import io.Source
+import scala.util.Using
+import scala.collection.mutable.ListBuffer
+
+type Lock = List[Int]
+type Key = List[Int]
+
+def readLocksAndKeys(filename: String) =
+  val tmp = Using(Source.fromFile(filename)) {
+    _.getLines.foldLeft((List[List[String]](), List[String]())) { (acc, l) =>
+      val (schemas, currentSchema) = acc
+      if l.isEmpty then (schemas :+ currentSchema, List[String]())
+      else (schemas, currentSchema :+ l)
+    }
+  }.get
+  val schemas = tmp._1 :+ tmp._2
+
+  schemas.foldLeft((List[Lock](), List[Lock]())) {
+    (lockAndKeyAcc, schemaLines) =>
+      val (locks, keys) = lockAndKeyAcc
+      val schema = (0 until schemaLines(0).length)
+        .map(i => schemaLines.filter(l => l(i) == '#').length - 1)
+        .toList
+
+      if schemaLines(0).forall(_ == '#') then (locks :+ schema, keys)
+      else (locks, keys :+ schema)
+  }
+
+def solve(locks: List[Lock], keys: List[Key]) =
+  locks
+    .map(lock =>
+      keys
+        .filter(key => lock.zip(key).map((l, k) => l + k).forall(_ <= 5))
+        .length
+    )
+    .sum
+
+@main def main(filename: String) =
+  val (locks, keys) = readLocksAndKeys(filename)
+  println(solve(locks, keys))