Sync

Task/Balanced-brackets/Scala/balanced-brackets-1.scala

@@ -0,0 +1,36 @@
+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))
+}

Task/Balanced-brackets/Scala/balanced-brackets-2.scala

@@ -0,0 +1,32 @@
+import scala.util.Random
+
+object BalancedParensApp extends App {
+
+  val triesCount = 10
+
+  (0 until triesCount).foreach { i =>
+    val str = randomString(length = i)
+    val msg = if (isBalanced(str)) "ok" else "NOT ok"
+    println(s"$str - $msg")
+  }
+
+  def randomString(length: Int) = {
+    val parensPairs = ("[]" * length).toSeq
+    val parensOfGivenLength = parensPairs.take(length)
+    val shuffledParens = Random.shuffle(parensOfGivenLength)
+    shuffledParens.mkString
+  }
+
+  def isBalanced(parensString: String): Boolean = {
+    var balance = 0
+    parensString.foreach { char =>
+      char match {
+        case '[' => balance += 1
+        case ']' => balance -= 1
+      }
+      if (balance < 0) return false;
+    }
+    balance == 0
+  }
+
+}