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Author: udaram

Doubly_linklist.py

@@ -0,0 +1,149 @@
+#Doubly Linklist implementation
+
+class Node:
+    def __init__(self,data):
+        self.data=data
+        self.next=None
+        self.prev=None
+
+# Doubly Link list class 
+class Doubly_linklist:
+    #constructor
+    def __init__(self):
+        self.head=None
+        self.tail=None
+    #funcion to insert in Doubly link list at end 
+    def insert(self,data):
+        a=Node(data)
+        if self.head is None:
+            self.head=self.tail=a
+        else:
+            self.tail.next=a
+            a.prev=self.tail
+            self.tail=a
+    #to insert node at begining of list
+    def insert_At_Beg(self,data):
+        a=Node(data)
+        if self.head is None:
+            self.head=self.tail=a
+        else :
+            a.next=self.head
+            self.head.prev=a
+            self.head=a
+    #Insertion at perticular Position 
+    def insert_At_Pos(self,pos,data):
+        a=Node(data)
+        p=self.head
+        i=0
+        if pos==0:
+            self.insert_At_Beg(data)
+        else:
+            while p!=None and pos-1!=i:
+                i+=1
+                p=p.next
+            if p is None and pos>i :
+                print("INVALID POSITION")
+            else:
+                a.prev=p
+                a.next=p.next
+                p.next.prev=a
+                p.next=a
+    #to display list
+    def display(self):
+        p=self.head
+        print("\nDoubly Link list is:::",end ="")
+        if p is None:
+            print("Empty!!!!")
+        while p is not None:
+            print("<=> ",p.data,end =" ")
+            p=p.next
+    #Display list in reverse order
+    def reverse(self):
+        p=self.tail
+        if p is None:
+            print("List is Empty")
+        else:
+            while p is not None:
+                print("<=>",p.data,end="")
+                p=p.prev
+    #delete the  starting node from List
+    def delete(self):
+        if self.head is None:
+            print("List is Empty")
+        else:
+            self.head=self.head.next
+            self.head.prev=None
+    #deletion from End
+    def delete_form_End(self):
+        if self.head is None:
+            print("List is Empty")
+        else:
+            self.tail=self.tail.prev
+            self.tail.next=None
+    #Deletion from a perticular position
+    def delete_From_Pos(self,pos):
+        if self.head==None:
+            print("List is Empty")
+        elif pos==0:
+            self.delete()
+        else:
+            p=self.head
+            i=0
+            while p!=None and pos-1 is not i:
+                i+=1
+                p=p.next
+            if p is None and pos>=i:
+                print("Invalid Position")
+            elif p.next.next is None and i is pos-1:
+                p.next=None
+                self.tail=p;
+            else:
+                p.next.next.prev=p
+                p.next=p.next.next
+                
+def main():
+    l=Doubly_linklist()
+    ch='y'
+    while ch is 'y':
+        print('''1.Insertion
+2.Insert at begining
+3.Insert at End 
+4.Insert at Position
+5.Display list
+6.Display in reverse order
+7.Delete from begining
+8.Delete from end
+9.Delete from position
+10.EXIT''')
+        
+        option=int(input("Enter option:::"))
+        
+        if option is 1:
+            a=int(input("Enter data::"))
+            l.insert(a)
+        elif option is 2:
+            a=int(input("Enter data::"))
+            l.insert_At_Beg(a)
+        elif option is 3:
+            a=int(input("Enter data::"))
+            l.insert(a)
+        elif option is 4:
+            pos=int(input("Enter Position(0 ......n)::"))
+            a=int(input("Enter data::"))
+            l.insert_At_Pos(pos,a)
+        elif option is 5:
+            l.display()
+        elif option is 6:
+            print("List in Reverse Order is :::",end="")
+            l.reverse()
+        elif option is 7:
+            l.delete()
+        elif option is 8:
+            l.delete_form_End()
+        elif option is 9:
+            pos=int(input("Enter Position(0 ......n)::"))
+            l.delete_From_Pos(pos)
+        else:
+            quit()
+        ch=input("\nEnter y to continue program:::")
+main()