1 files changed, 13 insertions, 2 deletions
diff --git a/Scala/example/src/main/scala/example/Lists.scala b/Scala/example/src/main/scala/example/Lists.scala
index 4e5feee..628486c 100644
--- a/Scala/example/src/main/scala/example/Lists.scala
+++ b/Scala/example/src/main/scala/example/Lists.scala
@@ -23,7 +23,11 @@ object Lists {
    * @param xs A list of natural numbers
    * @return The sum of all elements in `xs`
    */
-  def sum(xs: List[Int]): Int = ???
+  def sum(xs: List[Int]): Int = {
+    def sumIter(acc: Int, xs: List[Int]): Int =
+      if (xs.isEmpty) acc else sumIter(acc + xs.head, xs.tail)
+    sumIter(0, xs)
+  }
 
   /**
    * This method returns the largest element in a list of integers. If the
@@ -38,5 +42,12 @@ object Lists {
    * @return The largest element in `xs`
    * @throws java.util.NoSuchElementException if `xs` is an empty list
    */
-  def max(xs: List[Int]): Int = ???
+  def max(xs: List[Int]): Int = {
+    def maxInt(a: Int, b: Int) = if (a>b) a else b
+    def maxIter(max: Int, xs: List[Int]): Int =
+      if (xs.isEmpty) max else maxIter(maxInt(max,xs.head), xs.tail)
+    if (xs.isEmpty) throw new NoSuchElementException
+    else maxIter(Integer.MIN_VALUE, xs)
+  }
+
 }