added midterm preparation

src/MidTermPrep1/Ex2.sc

@@ -0,0 +1,20 @@
+import scala.annotation.tailrec
+
+def balanceMatch(chars: List[Char]): Boolean = {
+  @tailrec
+  def checkStep(chars: List[Char], n: Int): Boolean = {
+    if (chars.isEmpty) n == 0
+    else if (n < 0) false
+    else checkStep(chars.tail, chars.head match {
+      case '(' => n + 1
+      case ')' => n - 1
+      case _ => n
+    })
+  }
+  checkStep(chars, 0)
+}
+
+balanceMatch("(if (x == 0) then max (1, x))".toList)
+balanceMatch("I told him (that it's not (yet) done). (But he wasn't listening)".toList)
+balanceMatch(")".toList)
+balanceMatch("())()".toList)