From e709a4b5ea88c8f3f566c8c8cea95a3e529d52a4 Mon Sep 17 00:00:00 2001
From: Mahadev <Mahadev@thoughtworks.com>
Date: Tue, 26 Dec 2017 19:19:18 +0530
Subject: [PATCH] Add IndexOf method to SinglyLinkedList

---
 lists/singlylinkedlist/singlylinkedlist.go    | 12 +++++++++
 .../singlylinkedlist/singlylinkedlist_test.go | 27 +++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/lists/singlylinkedlist/singlylinkedlist.go b/lists/singlylinkedlist/singlylinkedlist.go
index 139925b..3182af3 100644
--- a/lists/singlylinkedlist/singlylinkedlist.go
+++ b/lists/singlylinkedlist/singlylinkedlist.go
@@ -154,6 +154,18 @@ func (list *List) Values() []interface{} {
 	return values
 }
 
+//IndexOf returns index of provided element
+func (list *List) IndexOf(value interface{}) int{
+	if list.size == 0 {
+		return -1
+	}
+	for index, element := range list.Values() {
+		if element == value {
+			return index
+		}
+	}
+	return -1
+}
 // Empty returns true if list does not contain any elements.
 func (list *List) Empty() bool {
 	return list.size == 0
diff --git a/lists/singlylinkedlist/singlylinkedlist_test.go b/lists/singlylinkedlist/singlylinkedlist_test.go
index 27daacc..0bebbb3 100644
--- a/lists/singlylinkedlist/singlylinkedlist_test.go
+++ b/lists/singlylinkedlist/singlylinkedlist_test.go
@@ -133,6 +133,33 @@ func TestListValues(t *testing.T) {
 	}
 }
 
+func TestListIndexOf(t *testing.T) {
+	list := New()
+
+	expectedIndex := -1
+	if index  := list.IndexOf("a"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+
+	list.Add("a")
+	list.Add("b", "c")
+
+	expectedIndex = 0
+	if index  := list.IndexOf("a"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+
+	expectedIndex = 1
+	if index  := list.IndexOf("b"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+
+	expectedIndex = 2
+	if index  := list.IndexOf("c"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+}
+
 func TestListInsert(t *testing.T) {
 	list := New()
 	list.Insert(0, "b", "c")