Merge pull request #733 from kumarankm/Dlinkedlist

Doubly linked list with python

Author: Saviour1001

Data Structures/Linked Lists/Doubly Linked List/d_linkedlist.py

@@ -0,0 +1,173 @@
+# Class for creating Node
+class Node:
+    def __init__(self, data=None, next=None, prev=None):
+        self.data = data
+        self.next = next
+        self.prev = prev
+
+# Double linkedlist area
+
+
+class DLinkedList:
+    # initializind head
+    def __init__(self):
+        self.head = None
+
+    # insertion at start
+    def addbeg(self, data):
+        if self.head == None:
+            node = Node(data, self.head, None)
+            self.head = node
+        else:
+            node = Node(data, self.head, None)
+            self.head.prev = node
+            self.head = node
+
+     # printing the list
+    def prinnt(self):
+        if self.head is None:
+            print('empty')
+            return
+        temp = self.head
+        st = ''
+        while temp:
+            st += '<-' + str(temp.data) + '->'
+            temp = temp.next
+        print(st)
+
+    # insertion at end
+    def addend(self, data):
+        if self.head is None:
+            self.head = Node(data, None, None)
+        else:
+            temp = self.head
+            while temp.next:
+                temp = temp.next
+            node = Node(data, None, temp)
+            temp.next = node
+
+    #printing in forward
+    def pforward(self):
+        if self.head is None:
+            print('empty')
+            return
+        temp = self.head
+        st = ''
+        while temp:
+            st += str(temp.data) + '->'
+            temp = temp.next
+        print(st)
+
+     # Finding the length of linkedlist
+    def lenn(self):
+        if self.head is None:
+            print('empty')
+            return
+        count = 0
+        temp = self.head
+        while temp:
+            count += 1
+            temp = temp.next
+        return count
+
+    # finding last node
+    def lastnode(self):
+        temp = self.head
+        while temp.next:
+            temp = temp.next
+        return temp
+
+    # Inserting element at linkedlist with index
+    def addmid(self, index, data):
+        if index < 0 or index >= self.lenn():
+            print('Invalid index')
+            return
+
+        if index == 0:
+            self.addbeg(data)
+            return
+
+        if index == self.lenn() - 1:
+            self.addend(data)
+            return
+
+        temp = self.head
+        count = 0
+        while temp:
+            if count == index - 1:
+                node = Node(data, temp.next, temp)
+                temp.next.prev = node
+                temp.next = node
+                break
+            temp = temp.next
+            count += 1
+
+    #print in reverse
+    def pbackward(self):
+        if self.head is None:
+            print('empty')
+            return
+        temp = self.lastnode()
+        st = ''
+        while temp:
+            st += '<-' + str(temp.data)
+            temp = temp.prev
+        print(st)
+
+    # removing element at linkedlist with index
+    def remove(self, index):
+
+        if index < 0 or index >= self.lenn():
+            print('Invalid index')
+            return
+        if index == 0:
+            self.head = self.head.next
+            self.head.prev.next = None
+            self.head.prev = None
+            return
+
+        if index == self.lenn() - 1:
+            temp = self.head
+            while temp.next:
+                temp = temp.next
+            temp.prev.next = None
+            temp.prev = None
+            return
+
+        temp = self.head
+        count = 0
+        while temp:
+            if count == index:
+                temp.prev.next = temp.next
+                temp.next.prev = temp.prev
+                temp.prev = None
+                temp.next = None
+
+            temp = temp.next
+            count += 1
+
+
+if __name__ == '__main__':
+    li = DLinkedList()
+    a = int(input('Enter the value to insert at beg: '))
+    li.addbeg(a)
+    b = int(input('Enter the value to insert at beg: '))
+    li.addbeg(b)
+    c = int(input('Enter the value to insert at end: '))
+    li.addend(c)
+    d = int(input('Enter the value to insert at end: '))
+    li.addend(d)
+    li.prinnt()
+    print("Priting in forward: ", end="")
+    li.pforward()
+    print('Printing in backward: ', end="")
+    li.pbackward()
+    print('Len of linked list is ', end='')
+    li.lenn()
+    e = int(input('Enter the index to be removed: '))
+    li.remove(e)
+    li.prinnt()
+    f = int(input('Enter the index: '))
+    g = int(input('Enter the number: '))
+    li.addmid(f, g)
+    li.prinnt()