added assignment 5 ex 2

src/Assignment5/Folds.sc

@@ -0,0 +1,36 @@
+def areTrue(booleans: List[Boolean]): Boolean = {
+  booleans.foldLeft(true)((acc, value) => acc && value)
+}
+
+def lString(strings: List[String]): Int = {
+  strings.foldLeft(0)((len, str) => len + str.length)
+}
+
+def longest(strings: List[String]): Int = {
+  strings.foldLeft(0)((maxLen, str) => if (str.length > maxLen) str.length else maxLen)
+}
+
+def isPresent[T](list: List[T], target: T): Boolean = {
+  list.foldLeft(false)((res, value) => res || value == target)
+}
+
+def flattenList(list: List[Any]): List[Any] = {
+  list.foldRight(List.empty[Any])((elem, acc) => {
+    elem match {
+      case l: List[Any] => flattenList(l).foldRight(acc)((e, l) => e::l)
+      case _ => elem::acc
+    }
+  })
+}
+
+assert(!areTrue(List(true, true, false)))
+assert(areTrue(List(true, true, true)))
+
+assert(lString(List("Folding", "is", "fun")) == 12)
+
+assert(longest(List("What", "is", "the", "longest?")) == 8)
+
+assert(!isPresent(List(1, 2, 3, 4), 5))
+assert(isPresent(List(1, 2, 3, 4), 3))
+
+assert(flattenList(List(List(1, 1), 2, List(3, List(5, 8)))) == List(1, 1, 2, 3, 5, 8))