Linked List Programs

Author: akhileshsantoshwar

Linked Lists/DoublyLinkedList.py

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+# Author: AKHILESH SANTOSHWAR
+
+class Node(object):
+    # Each node has its data and a pointer that points to next node in the Linked List
+    def __init__(self, data, next = None, previous = None):
+        self.data = data;
+        self.next = next;
+        self.previous = previous
+
+class DoublyLinkedList(object):
+    def __init__(self):
+        self.head = None
+
+    # for inserting at beginning of linked list
+    def insertAtStart(self, data):
+        if self.head == None:
+            newNode = Node(data)
+            self.head = newNode
+        else:
+            newNode = Node(data)
+            self.head.previous = newNode
+            newNode.next = self.head
+            self.head = newNode
+
+    # for inserting at end of linked list
+    def insertAtEnd(self, data):
+        newNode = Node(data)
+        temp = self.head
+        while(temp.next != None):
+            temp = temp.next
+        temp.next = newNode
+        newNode.previous = temp
+
+    # deleting a node from linked list
+    def delete(self, data):
+        temp = self.head
+        if(temp.next != None):
+            # if head node is to be deleted
+            if(temp.data == data):
+                temp.next.previous = None
+                self.head = temp.next
+                temp.next = None
+                return
+            else:
+                while(temp.next != None):
+                    if(temp.data == data):
+                        break
+                    temp = temp.next
+                if(temp.next):
+                    # if element to be deleted is in between
+                    temp.previous.next = temp.next
+                    temp.next.previous = temp.previous
+                    temp.next = None
+                    temp.previous = None
+                else:
+                    # if element to be deleted is the last element
+                    temp.previous.next = None
+                    temp.previous = None
+                return
+
+        if (temp == None):
+            return
+
+    # for printing the contents of linked lists
+    def printdll(self):
+        temp = self.head
+        while(temp != None):
+            print(temp.data, end=' ')
+            temp = temp.next
+
+if __name__ == '__main__':
+    dll = DoublyLinkedList()
+    dll.insertAtStart(1)
+    dll.insertAtStart(2)
+    dll.insertAtEnd(3)
+    dll.insertAtStart(4)
+    dll.printdll()
+    dll.delete(2)
+    print()
+    dll.printdll()