Conceptually adding two linked lists

[toomanystars]

Hi guys,

Yesterday, I recieved some help adding two linked lists of same length, and today I would like to tackle the problem of adding two different lengths. Example:

list 1: head->3->4->5->1->4;
list 2: head->4->3->1;

So if I start at both heads, I am fine until I reach list 2 Null. What do I need to consider, or do, to add list1's last two elements to list2's non existing last two elements?

If this was array, I would make a dummy array, set to zero and continue with the addition. Is there a similar method with linked lists to trick the compiler into addition?

Not really looking for code, just the methodology I need to apply and things to consider.

THanks,

Mike

[Catfish2]

Pseudocode (because you aren't "really looking for code"):

function add(listPointer1, listPointer2)
    while listPointer1 is not null or listPointer2 is not null
        valueToAdd := 0

        if listPointer1 is not null
            valueToAdd := valueToAdd + listPointer1.number
            listPointer1 := listPointer1.next
        endif

        if listPointer2 is not null
            valueToAdd := valueToAdd + listPointer2.number
            listPointer1 := listPointer2.next
        endif

        resultingList.add(valueToAdd)
    endwhile

    return resultingList
end function

Edit: minor corrections. If you have questions...

[Lowest0ne]

You might as well think about the case that list1 is shorter than list 2 also.

I guess you have a choice to make, does the addition of these two equal this:

list 3: head->7->7->6
or this:
list 3: head->7->7->6->1->4

First case is easier: While both nodes are not null, add the two together and increment both nodes.

2nd case has the same code as case one. But, when you reach a NULL node, you need to make new nodes and tack them onto list 3 from whichever list still has nodes left.