如何将节点添加到倒数第二个位置？

Question

So I'm trying to make a method that inserts a node at the second to last position of a linked list.

Ex - I want to place 2 in the second to last position of my list of [1,2,3], so my list would now be [1,2,2,3]

I tried the following code, but it doesn't seem to work.

public void addSecondToLast(int data){
    Node node = new Node();
    node.data = data;
    node.next = null;

    if(top == null){
        node = top;
    }
    if(top.next == null){
        node = top.next;
    }
    else {
        Node temp = new Node();
        Node prev = new Node();
        temp = top;

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


    }

Answer 1

In the else statement where you're assigning prev = node, it should be prev.next = node, as prev is the current second to the last, now the node will take its place, so point prev to node and join node to the last node of linked list. Try this, it should work.

first->prev->last, now your new node should be between prev and last, so first->prev->node->last