Merge pull request #1 from nazuk27/nazuk27-patch-1

Added Reverse a doubly linked list (Python) aditya109#283

Programming/Python/ReverseDoublyLinkedList/ReverseDoublyLinkedList.py

@@ -0,0 +1,72 @@
+#!/bin/python3
+
+# Program to inplement reversal of a Doubly LinkedList.
+
+import math
+import os
+import random
+import re
+import sys
+
+class DoublyLinkedListNode:
+    def __init__(self, node_data):
+        self.data = node_data
+        self.next = None
+        self.prev = None
+
+class DoublyLinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def insert_node(self, node_data):
+        node = DoublyLinkedListNode(node_data)
+
+        if not self.head:
+            self.head = node
+        else:
+            self.tail.next = node
+            node.prev = self.tail
+
+
+        self.tail = node
+
+def print_doubly_linked_list(node, sep):
+    while node:
+        print(str(node.data), end=' ')
+        node = node.next
+
+
+# DoublyLinkedListNode:
+#     int data
+#     DoublyLinkedListNode next
+#     DoublyLinkedListNode prev
+
+def reverse(head):
+    r = head
+    p = None
+    while r!=None:
+        q = r.next
+        r.next = p
+        r.prev = q
+        p = r
+        r = q
+    return p
+
+
+if __name__ == '__main__':
+    t = int(input())
+
+    for t_itr in range(t):
+        llist_count = int(input())
+
+        llist = DoublyLinkedList()
+
+        for _ in range(llist_count):
+            llist_item = int(input())
+            llist.insert_node(llist_item)
+
+        llist1 = reverse(llist.head)
+
+        print_doubly_linked_list(llist1, ' ')
+