using ref to delete Node in the middle of a linked list, given only access to that node

Question

I have the solution. So I do not need help, but I have a question. This code works:

public void Delete(ref Node n)
{
    n = n.next;
}

LinkedList list = new LinkedList();
list.AddTail(4);
list.AddTail(3);
list.AddTail(2);
list.AddTail(1);
list.AddTail(0);

list.Delete(ref list.head.next.next);

But this code does not:

Node n = list.head.next.next;
list.Delete(ref n);

Why?

EDIT:

public class Node
{
    public int number;
    public Node next;

    public Node(int number, Node next)
    {
        this.number = number;
    }
}

I think it's not working because in the first case you are changing the next property of list.head.next but in the second case you are just changing the node that your local variable n is referencing. — Mark
– Mark, Commented Feb 9, 2016 at 12:23

Alex · Accepted Answer · 2016-02-09 12:31:44Z

0

When you call

list.Delete(ref list.head.next.next);

You change reference (pointer) to field List.next.

But if you call

list.Delete(ref n);

You change reference (pointer) of local variable.

Just try to inline you code:

list.Delete(ref list.head.next.next);

looks like

list.head.next.next = list.head.next.next.next;

But

Node n = list.head.next.next; 
list.Delete(ref n);

looks like

Node n = list.head.next.next; 
n = n.next;

answered Feb 9, 2016 at 12:31

Alex

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