Sheffield | 25-SDC-Nov | Hassan Osman | Sprint 2 | Implement a linked list in Python

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,74 @@
+class Node:
+    def __init__(self, data):
+        self.data = data
+        self.previous = None
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, data):
+        new_head_node = Node(data)
+        if self.head is not None:
+            new_head_node.next = self.head
+            self.head.previous = new_head_node
+
+        self.head = new_head_node
+        if self.tail is None:
+            self.tail = new_head_node
+
+        return new_head_node
+
+
+
+    def pop_tail(self):
+        if self.tail is None:
+            raise IndexError("Unable to remove from empty linked list")
+
+        tail_node = self.tail
+        previous = self.tail.previous
+
+        self.tail = previous
+        if self.tail is not None:
+            self.tail.next = None
+        else:
+            self.head = None
+
+        tail_node.previous = None
+        tail_node.next = None
+
+        return tail_node.data
+
+
+
+    def remove(self, node):
+        previous_node = node.previous
+        next_node = node.next
+
+        if node.previous is not None:
+            previous_node.next = next_node
+        else:
+            self.head = next_node
+
+        if node.next is not None:
+            next_node.previous = previous_node
+        else:
+            self.tail = previous_node
+
+        node.previous = None
+        node.next = None
+
+
+
+
+
+
+
+
+
+
+
+
+

Sprint-2/implement_linked_list/linked_list_test.py

@@ -34,6 +34,20 @@ def test_remove_tail(self):
         self.assertIsNone(b.next)
         self.assertIsNone(b.previous)
 
+    def test_remove_middle(self):
+        l = LinkedList()
+        l.push_head("a")
+        b = l.push_head("b")
+        l.push_head("c")
+
+        l.remove(b)
+
+        self.assertIsNone(b.next)
+        self.assertIsNone(b.previous)
+
+        self.assertEqual(l.pop_tail(), "a")
+        self.assertEqual(l.pop_tail(), "c")
+
 
 if __name__ == "__main__":
     unittest.main()