Thread: LinkedList operator= and deep copy

Ok so I wrote my own (doubly) linked list class.
I want to implement the copy ctor, and operator=.

The list we are copying to may not be empty when operator= is called, so what do we do?
Do we clear the list?
Or do we use the nodes we already have, and copy the data into those node's?

The problem I see with clearing the list, is that clearing is a linear O(n), operation, and so is the copying (cloning if you will). So that would make operator= quadratic (right?).
Quadratic is unacceptable. Copying should be linear.

So how does the standard library do this?
And more importantly what should I do to implement operator=?

Copy ctor isn't a big deal because the list we are copying to is empty.


Here is some code to demonstrate what I mean:

Code:

    LinkedList<int> srcList;
    
    srcList.Append(1);
    srcList.Append(2);
    srcList.Append(3);

    // create dest list

    LinkedList<int> destList;

    // add values to dest list

    destList.Append(4);
    destList.Append(5);
    
    // dest list isn't empty.....

    destList = srcList;