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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

  • Elnaz + 4 comments

    Java implementation :

    if (head == null){
        head = new Node();
        head.data = data;
    }
    else {
        Node node = head;
        while (node.next != null){
            node = node.next;
        }
        node.next = new Node();
        node.next.data = data;
    }
    return head;
    • shahab03 + 1 comment

      what does this do?

      while (node.next != null){ node = node.next; }

      and why is it needed?

      • Elnaz + 0 comments

        The while loop first check if current node next is not null, it traverse the current node to the second node and when current node next become null, current node point to the last node!

    • The_Speck + 1 comment

      Why must you declare a "Node node = head"? Initially I had:

      if(head == null)
    {
        head = new Node();
        head.data = data;
    }
    else{
        while(head.next != null) head = head.next;
        head.next = new Node();
        head.next.data = data;
    }
    return head;

      But this method doesn't work. May you explain why? Thank you!

      • sanipatel2141 + 1 comment

        because the question asks to "return the head of the updated linked list". In your case you're returning the pointer (is that correct Java terminology?) to the last node.

        • vishaltk + 0 comments

          I did the same mistake, initially and was scratching my head to figured where I went wrong. Hence people say understanding the requirement is important. You may right functionally correct code, but if that is not meeting the requirement, then the whole purpose of your program/app is defeated.

    • haripriya_sreer1 + 1 comment
      [deleted]
      • shaikhkamal2012 + 0 comments

        Hope this will work in c SinglyLinkedListNode *ptr,*tmp; tmp = (SinglyLinkedListNode *)malloc(sizeof(SinglyLinkedListNode)); tmp->data = data;

        if(head==NULL){
    head=tmp;
    tmp->next = NULL;
    return head;
}
else{
    ptr=head;
    while(ptr->next!= NULL)
        ptr=ptr->next;
    ptr->next = tmp;
    tmp->next = NULL;
}

return head;
    • cmveal + 0 comments

      Better to track the last node rather than constantly looping over the list.

      static SinglyLinkedListNode last = null;

static SinglyLinkedListNode insertNodeAtTail(SinglyLinkedListNode head, int data) {
    SinglyLinkedListNode newNode = new SinglyLinkedListNode(data);
    if (head == null) {
        head = newNode;
        last = newNode;
    } else {
        last.next = newNode;
        last = newNode;
    }
    return head;
}