From 092a1156420be4121b99a6ba2e75365da66a4ec9 Mon Sep 17 00:00:00 2001
From: Emir Pasic <emirpasic@hotmail.com>
Date: Fri, 13 Mar 2015 00:06:49 +0100
Subject: [PATCH] - add swap method to arraylist (consider adding this on all
 lists)

---
 README.md                         | 7 ++++---
 examples/arraylist.go             | 5 +++--
 lists/arraylist/arraylist.go      | 7 +++++++
 lists/arraylist/arraylist_test.go | 7 +++++++
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index 8a7d37f..021b7d2 100644
--- a/README.md
+++ b/README.md
@@ -168,13 +168,14 @@ func main() {
 	list := arraylist.New()
 	list.Add("a")                         // ["a"]
 	list.Add("c", "b")                    // ["a","c","b"]
-    list.Sort(utils.StringComparator)     // ["a","b","c"]
+	list.Sort(utils.StringComparator)     // ["a","b","c"]
 	_, _ = list.Get(0)                    // "a",true
 	_, _ = list.Get(100)                  // nil,false
 	_ = list.Contains("a", "b", "c")      // true
 	_ = list.Contains("a", "b", "c", "d") // false
-	list.Remove(2)                        // ["a","b"]
-	list.Remove(1)                        // ["a"]
+	list.Swap(0, 1)                       // ["b","a",c"]
+	list.Remove(2)                        // ["b","a"]
+	list.Remove(1)                        // ["b"]
 	list.Remove(0)                        // []
 	list.Remove(0)                        // [] (ignored)
 	_ = list.Empty()                      // true
diff --git a/examples/arraylist.go b/examples/arraylist.go
index 877e623..f2134c7 100644
--- a/examples/arraylist.go
+++ b/examples/arraylist.go
@@ -40,8 +40,9 @@ func ArrayListExample() {
 	_, _ = list.Get(100)                  // nil,false
 	_ = list.Contains("a", "b", "c")      // true
 	_ = list.Contains("a", "b", "c", "d") // false
-	list.Remove(2)                        // ["a","b"]
-	list.Remove(1)                        // ["a"]
+	list.Swap(0, 1)                       // ["b","a",c"]
+	list.Remove(2)                        // ["b","a"]
+	list.Remove(1)                        // ["b"]
 	list.Remove(0)                        // []
 	list.Remove(0)                        // [] (ignored)
 	_ = list.Empty()                      // true
diff --git a/lists/arraylist/arraylist.go b/lists/arraylist/arraylist.go
index c87dac9..6473332 100644
--- a/lists/arraylist/arraylist.go
+++ b/lists/arraylist/arraylist.go
@@ -142,6 +142,13 @@ func (list *List) Sort(comparator utils.Comparator) {
 	utils.Sort(list.elements[:list.size], comparator)
 }
 
+// Swaps two elements with 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]
+	}
+}
+
 func (list *List) String() string {
 	str := "ArrayList\n"
 	values := []string{}
diff --git a/lists/arraylist/arraylist_test.go b/lists/arraylist/arraylist_test.go
index 5b1e30a..1844e27 100644
--- a/lists/arraylist/arraylist_test.go
+++ b/lists/arraylist/arraylist_test.go
@@ -73,6 +73,13 @@ func TestArrayList(t *testing.T) {
 		t.Errorf("Got %v expected %v", actualValue, "c")
 	}
 
+	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 {