add tail to linked list

data_structures/linkedlist.py

@@ -9,6 +9,7 @@ def __str__(self):
 class LinkedList:
     def __init__(self):
         self.head = None
+        self.tail = None
 
     def get_i(self, i):
         # return the value at index i
@@ -21,16 +22,13 @@ def append(self, value):
         '''Add a new node with the value value to the end of the list'''
         # Create a new node
         new_node = Node(value)
-        print(new_node)
-
+
         if self.head == None:
             self.head = new_node
-        else:
-            # Find the last node
-            cur = self.head
-            while cur.next != None:
-                cur = cur.next
-            cur.next = new_node
+            self.tail = new_node
+
+        self.tail.next = new_node
+        self.tail = new_node
 
     def insert(self, value, i):
         '''Insert a node with the value value at index i'''
@@ -39,12 +37,16 @@ def insert(self, value, i):
         if i == 0:
             new_node.next = self.head
             self.head = new_node
+
         else:
             cur = self.head
             for j in range(i-1):
                 cur = cur.next
             new_node.next = cur.next
             cur.next = new_node
+
+        if new_node.next == None:
+            self.tail = new_node
 
     def __str__(self):
         cur = self.head