Added doubly linked list div-bargali#158

Added doubly linked list div-bargali#158

Author: div-bargali

Python/Data-Structures/Doubly Linked List/doublylist.py

@@ -0,0 +1,94 @@
+class Node:
+ def __init__(self, data=None, prev=None, next=None):
+ self.data = data
+ self.prev = prev
+ self.next = next
+
+
+class Doublylist:
+ def __init__(self):
+ self.head = None
+
+ def insertatbeginning(self, data):
+ if self.head is None:
+ node = Node(data)
+ self.head = node
+ else:
+ self.head = Node(data, next=self.head)
+
+ def length(self):
+ itr = self.head
+ count = 0
+ while itr:
+ count += 1
+ itr = itr.next
+ return count
+
+ def insertatend(self, data):
+ if self.head is None:
+ self.insertatbeginning(data)
+ else:
+ itr = self.head
+ while itr.next:
+ itr = itr.next
+ itr.next = Node(data, prev=itr)
+
+ def print(self):
+ itr = self.head
+ istr = ''
+ while itr:
+ istr += str(itr.data) + '-->'
+ itr = itr.next
+ print(istr)
+
+ def insertat(self, data, at):
+ if at == 0:
+ self.insertatbeginning(data)
+ elif at == self.length() - 1:
+ self.insertatend(data)
+ else:
+ itr = self.head
+ count = 0
+ while itr:
+ if count != at - 1:
+ count += 1
+ itr = itr.next
+ else:
+ break
+ itr.next = Node(data, itr, itr.next)
+
+ def removeval(self,val):
+ if self.head is None:
+ raise Exception("invalid list")
+ if self.head.data is val:
+ self.head = None
+ itr1=self.head
+ itr2=self.head
+ while itr1.next:
+ itr1=itr1.next
+ if itr1.data == val:
+ itr2.next=itr1.next
+ itr1.next.prev=itr2
+ itr2=itr2.next
+
+ def insertval(self,datalist):
+ for i in datalist:
+ d.insertatend(i)
+ return
+
+
+
+if __name__ == "__main__":
+ d = Doublylist()
+ d.insertatbeginning(5)
+ d.print()
+ d.insertatbeginning(6)
+ d.print()
+ print(d.length())
+ d.insertatend(20)
+ d.print()
+ d.insertat(4, 1)
+ d.removeval(6)
+ d.print()
+ d.removeval(4)
+ d.print()