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Task/Balanced-brackets/Scala/balanced-brackets.scala

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+import scala.collection.mutable.ListBuffer
+import scala.util.Random
+
+object BalancedBrackets extends App {
+
+  val random = new Random()
+  def generateRandom: List[String] = {
+    import scala.util.Random._
+    val shuffleIt: Int => String = i => shuffle(("["*i+"]"*i).toList).foldLeft("")(_+_)
+    (1 to 20).map(i=>(random.nextDouble*100).toInt).filter(_>2).map(shuffleIt(_)).toList
+  }
+
+  def generate(n: Int): List[String] = {
+    val base = "["*n+"]"*n
+    var lb = ListBuffer[String]()
+    base.permutations.foreach(s=>lb+=s)
+    lb.toList.sorted
+  }
+
+  def checkBalance(brackets: String):Boolean = {
+    def balI(brackets: String, depth: Int):Boolean = {
+      if (brackets == "") depth == 0
+      else brackets(0) match {
+        case '[' => ((brackets.size > 1) && balI(brackets.substring(1), depth + 1))
+        case ']' => (depth > 0) && ((brackets.size == 1) || balI(brackets.substring(1), depth -1))
+        case _   => false
+      }
+    }
+    balI(brackets, 0)
+  }
+
+  println("arbitrary random order:")
+  generateRandom.map(s=>Pair(s,checkBalance(s))).foreach(p=>println((if(p._2) "balanced:   " else "unbalanced: ")+p._1))
+  println("\n"+"check all permutations of given length:")
+  (1 to 5).map(generate(_)).flatten.map(s=>Pair(s,checkBalance(s))).foreach(p=>println((if(p._2) "balanced:   " else "unbalanced: ")+p._1))
+}