linked list - progress update

README.md

@@ -660,8 +660,8 @@ if you can identify the runtime complexity of different algorithms. It's a super
         - [x] push_back(value) - adds an item at the end
         - [x] pop_back() - removes end item and returns its value
         - [x] front() - get value of front item
-        - [ ] back() - get value of end item
-        - [ ] insert(index, value) - insert value at index, so current item at that index is pointed to by new item at index
+        - [x] back() - get value of end item
+        - [x] insert(index, value) - insert value at index, so current item at that index is pointed to by new item at index
         - [ ] erase(index) - removes node at given index
         - [ ] value_n_from_end(n) - returns the value of the node at nth position from the end of the list
         - [x] reverse() - reverses the list

learn_python/implementig_linked_list/models/linked_list.py

@@ -91,12 +91,49 @@ class LinkedList:
                 index -= 1
             return node.get_value()
 
+    def insert(self, index, value):
+        if index > self.size() or index < 0:
+            raise IndexError(index)
+        if index == 0:
+            self.push_front(value)
+            return
+        if self.size() == 1 and index == 1:
+            self.push_back(value)
+            return
+        else:
+            cur_index = 0
+            node = self.__head
+            prev = node
+            while cur_index != index and node.get_next() is not None:
+                cur_index += 1
+                prev = node
+                node = node.get_next()
+            if cur_index != index:
+                raise IndexError(index)
+            else:
+                new_node = ListNode(value)
+                new_node.set_next(node)
+                prev.set_next(new_node)
+                self.__size += 1
+
     def front(self):
-        "get value of front item"
+        "get value of the first item"
         if self.size() == 0:
             raise ListIsEmptyError
         return self.__head.get_value()
 
+    def back(self):
+        "get value of the last item"
+        if self.size() == 0:
+            raise ListIsEmptyError
+        if self.size() == 1:
+            return self.__head.get_value()
+        else:
+            node = self.__head
+            while node.get_next() is not None:
+                node = node.get_next()
+            return node.get_value()
+
     def reverse(self):
         if self.size() == 0 or self.size() == 1:
             pass
@@ -108,3 +145,10 @@ class LinkedList:
                 node = node.get_next()
             self.__head = reversed_list.__head
 
+    def print(self):
+        str = ""
+        node = self.__head
+        while node is not None:
+            str = f'{str} {node.get_value()}'
+            node = node.get_next()
+        return str.strip()

learn_python/implementig_linked_list/tests/linked_list_tests.py

@@ -71,6 +71,24 @@ class LinkedListTestCase(unittest.TestCase):
         value = linked_list.pop_front()
         self.assertEqual(value, 3)
 
+    def test_should_get_back_item(self):
+        linked_list = LinkedList()
+        linked_list.push_front(1)
+        linked_list.push_front(2)
+        linked_list.push_front(3)
+        value = linked_list.back()
+        self.assertEqual(value, 1)
+
+    def test_insert(self):
+        linked_list = LinkedList()
+        linked_list.insert(0, 1)
+        linked_list.insert(1, 2)
+        linked_list.insert(1, 5)
+        output = "1 5 2"
+        printed = linked_list.print()
+        self.assertEqual(output, printed)
+
+
 
 if __name__ == '__main__':
     unittest.main()