added balanceMatch moustache

src/MidTermPrep1/Ex2.sc

@@ -14,7 +14,23 @@ def balanceMatch(chars: List[Char]): Boolean = {
   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)
+def balanceMatch2(chars: List[Char]): Boolean = {
+  @tailrec
+  def checkStep(chars: List[Char], n: Int): Boolean = {
+    chars match {
+      case Nil => n == 0
+      case _ if n < 0 => false
+      case '('::rest => checkStep(rest, n + 1)
+      case ')'::rest => checkStep(rest, n - 1)
+      case _::rest => checkStep(rest, n)
+    }
+  }
+  checkStep(chars, 0)
+}
+
+balanceMatch2("(if (x == 0) then max (1, x))".toList)
+balanceMatch2("I told him (that it's not (yet) done). (But he wasn't listening)".toList)
+balanceMatch2(")".toList)
+balanceMatch2("())()".toList)
+balanceMatch2("())(()".toList)
+balanceMatch2("(".toList)