Fixed Issue aalhour#139 A new SkipList<int> contains 0

Author: Gutsonok

DataStructures/Lists/SkipList.cs

@@ -194,15 +194,20 @@ public bool Remove(T item, out T deleted)
         /// </summary>
         public bool Contains(T item)
         {
-            T itemOut;
-            return Find(item, out itemOut);
+            return Find(item, out var _);
         }
 
         /// <summary>
         /// Look for an element and return it if found
         /// </summary>
         public bool Find(T item, out T result)
         {
+            result = default;
+            if(IsEmpty)
+            {
+                return false;
+            }
+
             var current = _firstNode;
 
             // Walk after all the nodes that have values less than the node we are looking for
@@ -219,7 +224,6 @@ public bool Find(T item, out T result)
                 return true;
             }
 
-            result = default(T);
             return false;
         }
 

UnitTest/DataStructuresTests/SkipListTest.cs

@@ -6,6 +6,16 @@ namespace UnitTest.DataStructuresTests
 {
     public static class SkipListTest
     {
+        [Fact]
+        public static void EmptyList()
+        {
+            var skipList = new SkipList<int>();
+
+            Assert.True(skipList.Count == 0);
+            Assert.True(skipList.IsEmpty);
+            Assert.DoesNotContain(0, skipList);
+        }
+
         [Fact]
         public static void AddOneElement()
         {