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  1. Practice
  2. Data Structures
  3. Linked Lists
  4. Insert a Node at the Tail of a Linked List
  5. Discussions

Insert a Node at the Tail of a Linked List

  • jjenner689 + 8 comments

    I have a recursive solution in Python if anyone is interested:

    def Insert(head, data):
    if head == None:
        return Node(data, None)
    else:
        if head.next == None:
            head.next = Node(data,None)
        else:
            Insert(head.next,data)
        return head
    • fcorvese + 0 comments

      Thank you! In the 'else' case, I was returning the 'Insert' result and I see why that is incorrect now.

    • SirLemuel + 1 comment

      In the 3rd line you return a new Node object. I thought we were supposed to return only the head object. Can you explain this part? My understanding with linked list is that the head never has any data but is used to reference the first element in the list, yet you return a single Node with data and no head.

      • xiangyu_li1990 + 0 comments

        I can explain. The third line return the newest Node as the inserted node to the linked list because the program has already checked the head is Null. Returning the newest node would be the answer

    • siddharth9200 + 0 comments

      Nice use of the floating recursive call.

    • priya12345 + 0 comments

      nice code

    • SuperGogeta + 3 comments

      I did it non recursively, calling a function multiple times unless necessary would be inefficient.

      def Insert(head, data):
    if head == None:
        return Node(data,None)
    temp = head
    while temp != None:
        prevFinalNode=temp
        temp = temp.next
    prevFinalNode.next = Node(data,None)
    return head

      Also you could have used elif instead of else>if/else as such

      def Insert(head, data):
    if head == None:
        return Node(data, None)
    elif head.next == None:
        head.next = Node(data,None)
    else:
        Insert(head.next,data)
    return head

      The code looks more readable this way I think, sorry for the nitpicking.

      • DanHaggard + 1 comment

        I think you can trim one line out of your non-recursive solution:

        def Insert(head, data):
    if head == None:
        return Node(data, None)
    curr_node = head
    while curr_node.next != None:
        curr_node = curr_node.next
    curr_node.next = Node(data, None)
    return head
        • psykosh + 0 comments

          My code is basically the same other than naming and using "is/is not" for testing if None...

          and it's failing.

          def Insert(head, data):
    if head is None:
        return Node(data)
    here = head
    while here.next is not None:
        here = here.next
    here.next = Node(data)
    return head
      • thedurphy + 0 comments

        If we are nitpicking, setting the second argument in Node to None shouldn't be necessary since the default is already set to None.

      • petitjhn + 0 comments

        could you kindly explain line 4 and 5

    • desaim + 0 comments

      Nice! Good to see how to solve this problem in different ways.

    • subhsamal + 0 comments

      But Would you please clear one doubt! How is head able to use next attribute? Node class object only can have it, right ?

    • ritikagupta8734 + 0 comments

      why u returned head ? in last line u can return head.next ?