add swap method on all lists

lists/arraylist/arraylist.go

@@ -142,7 +142,7 @@ func (list *List) Sort(comparator utils.Comparator) {
 	utils.Sort(list.elements[:list.size], comparator)
 }
 
-// Swaps two elements with the given indices.
+// Swaps values of two elements at the given indices.
 func (list *List) Swap(i, j int) {
 	if list.withinRange(i) && list.withinRange(j) {
 		list.elements[i], list.elements[j] = list.elements[j], list.elements[i]

lists/doublylinkedlist/doublylinkedlist.go

@@ -228,6 +228,22 @@ func (list *List) Sort(comparator utils.Comparator) {
 
 }
 
+// Swaps values of two elements at the given indices.
+func (list *List) Swap(i, j int) {
+	if list.withinRange(i) && list.withinRange(j) && i != j {
+		var element1, element2 *element
+		for e, currentElement := 0, list.first; element1 == nil || element2 == nil; e, currentElement = e+1, currentElement.next {
+			switch e {
+			case i:
+				element1 = currentElement
+			case j:
+				element2 = currentElement
+			}
+		}
+		element1.value, element2.value = element2.value, element1.value
+	}
+}
+
 func (list *List) String() string {
 	str := "DoublyLinkedList\n"
 	values := []string{}

lists/doublylinkedlist/doublylinkedlist_test.go

@@ -37,16 +37,7 @@ func TestDoublyLinkedList(t *testing.T) {
 
 	list.Sort(utils.StringComparator)
 
-	list.Add("g", "a")
+	list.Add("e", "f", "g", "a", "b", "c", "d")
-	list.Append("b", "c", "d")
-	list.Prepend("e", "f")
-
-	shouldBe := []interface{}{"e", "f", "g", "a", "b", "c", "d"}
-	for i, _ := range shouldBe {
-		if value, ok := list.Get(i); value != shouldBe[i] || !ok {
-			t.Errorf("List not populated in correct order. Expected: %v Got: %v", shouldBe, list.Values())
-		}
-	}
 
 	list.Sort(utils.StringComparator)
 	for i := 1; i < list.Size(); i++ {
@@ -82,6 +73,14 @@ func TestDoublyLinkedList(t *testing.T) {
 		t.Errorf("Got %v expected %v", actualValue, "c")
 	}
 
+	list.Swap(0, 2)
+	list.Swap(0, 2)
+	list.Swap(0, 1)
+
+	if actualValue, ok := list.Get(0); actualValue != "b" || !ok {
+		t.Errorf("Got %v expected %v", actualValue, "c")
+	}
+
 	list.Remove(2)
 
 	if actualValue, ok := list.Get(2); actualValue != nil || ok {
@@ -101,9 +100,9 @@ func TestDoublyLinkedList(t *testing.T) {
 
 	list.Add("a", "b", "c")
 
-	//if actualValue := list.Contains("a", "b", "c"); actualValue != true {
+	if actualValue := list.Contains("a", "b", "c"); actualValue != true {
-	//	t.Errorf("Got %v expected %v", actualValue, true)
+		t.Errorf("Got %v expected %v", actualValue, true)
-	//}
+	}
 
 	if actualValue := list.Contains("a", "b", "c", "d"); actualValue != false {
 		t.Errorf("Got %v expected %v", actualValue, false)
@@ -111,9 +110,9 @@ func TestDoublyLinkedList(t *testing.T) {
 
 	list.Clear()
 
-	//if actualValue := list.Contains("a"); actualValue != false {
+	if actualValue := list.Contains("a"); actualValue != false {
-	//	t.Errorf("Got %v expected %v", actualValue, false)
+		t.Errorf("Got %v expected %v", actualValue, false)
-	//}
+	}
 
 	if actualValue, ok := list.Get(0); actualValue != nil || ok {
 		t.Errorf("Got %v expected %v", actualValue, false)

lists/lists.go

@@ -29,6 +29,7 @@ type Interface interface {
 	Add(elements ...interface{})
 	Contains(elements ...interface{}) bool
 	Sort(comparator utils.Comparator)
+	Swap(index1, index2 int)
 
 	containers.Interface
 	// Empty() bool

lists/singlylinkedlist/singlylinkedlist.go

@@ -207,6 +207,22 @@ func (list *List) Sort(comparator utils.Comparator) {
 
 }
 
+// Swaps values of two elements at the given indices.
+func (list *List) Swap(i, j int) {
+	if list.withinRange(i) && list.withinRange(j) && i != j {
+		var element1, element2 *element
+		for e, currentElement := 0, list.first; element1 == nil || element2 == nil; e, currentElement = e+1, currentElement.next {
+			switch e {
+			case i:
+				element1 = currentElement
+			case j:
+				element2 = currentElement
+			}
+		}
+		element1.value, element2.value = element2.value, element1.value
+	}
+}
+
 func (list *List) String() string {
 	str := "SinglyLinkedList\n"
 	values := []string{}

lists/singlylinkedlist/singlylinkedlist_test.go

@@ -37,16 +37,7 @@ func TestSinglyLinkedList(t *testing.T) {
 
 	list.Sort(utils.StringComparator)
 
-	list.Add("g", "a")
+	list.Add("e", "f", "g", "a", "b", "c", "d")
-	list.Append("b", "c", "d")
-	list.Prepend("e", "f")
-
-	shouldBe := []interface{}{"e", "f", "g", "a", "b", "c", "d"}
-	for i, _ := range shouldBe {
-		if value, ok := list.Get(i); value != shouldBe[i] || !ok {
-			t.Errorf("List not populated in correct order. Expected: %v Got: %v", shouldBe, list.Values())
-		}
-	}
 
 	list.Sort(utils.StringComparator)
 	for i := 1; i < list.Size(); i++ {
@@ -82,6 +73,14 @@ func TestSinglyLinkedList(t *testing.T) {
 		t.Errorf("Got %v expected %v", actualValue, "c")
 	}
 
+	list.Swap(0, 2)
+	list.Swap(0, 2)
+	list.Swap(0, 1)
+
+	if actualValue, ok := list.Get(0); actualValue != "b" || !ok {
+		t.Errorf("Got %v expected %v", actualValue, "c")
+	}
+
 	list.Remove(2)
 
 	if actualValue, ok := list.Get(2); actualValue != nil || ok {
@@ -101,9 +100,9 @@ func TestSinglyLinkedList(t *testing.T) {
 
 	list.Add("a", "b", "c")
 
-	//if actualValue := list.Contains("a", "b", "c"); actualValue != true {
+	if actualValue := list.Contains("a", "b", "c"); actualValue != true {
-	//	t.Errorf("Got %v expected %v", actualValue, true)
+		t.Errorf("Got %v expected %v", actualValue, true)
-	//}
+	}
 
 	if actualValue := list.Contains("a", "b", "c", "d"); actualValue != false {
 		t.Errorf("Got %v expected %v", actualValue, false)
@@ -111,9 +110,9 @@ func TestSinglyLinkedList(t *testing.T) {
 
 	list.Clear()
 
-	//if actualValue := list.Contains("a"); actualValue != false {
+	if actualValue := list.Contains("a"); actualValue != false {
-	//	t.Errorf("Got %v expected %v", actualValue, false)
+		t.Errorf("Got %v expected %v", actualValue, false)
-	//}
+	}
 
 	if actualValue, ok := list.Get(0); actualValue != nil || ok {
 		t.Errorf("Got %v expected %v", actualValue, false)