London | 25-SDC-July | Mikiyas Gebremichael | Sprint 2 | Implement a linked list in Python

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,47 @@
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+        self.previous = None
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+    def push_head(self, value): #this is to add a value/node to the head/start.
+        node = Node(value)
+        node.next = self.head
+        if self.head:
+            self.head.previous = node
+        self.head = node
+        if not self.tail:
+            self.tail = node #list=empty,tail also points to new node
+        return node
+    def pop_tail(self): #Remove the value from the tail of the list
+        if not self.tail:
+            return None 
+        value = self.tail.value
+        prev_node = self.tail.previous
+        if prev_node:
+            prev_node.next = None
+        self.tail = prev_node
+        if not self.tail:
+            self.head = None #If only one element is removed.
+        return value
+    def remove(self, node): #remove any node 
+        if not node:
+            return
+        prev_node = node.previous
+        next_node = node.next
+        if prev_node:
+            prev_node.next = next_node
+        else:
+            self.head = next_node
+        if next_node:
+            next_node.previous = prev_node
+        else:
+            self.tail = prev_node
+        node.next = None     #Disconnecting the node from the rest
+        node.previous = None
+# My analysis
+# the algorithm used on this linked list is efficient each methods have only O(1) space and time complexity since they operate on a single node at a time
+# and at the start of the program we just created a class at a time with similar time and space complexity of O(n)