An Introduction to Data Structures

Implementing Linked Lists (Implementing Insertion and Removal)

For the push_back function, we must first make a new node.
```
Node* newnode = new Node(s);
```
The node must point back to the old end of the list, while the old end must point to it.
```
newnode->previous = last;
last->next = newnode;
last= newnode;
```

There is a special case when last is NULL (the list is empty).

if (last == NULL)
{
   first = newnode;
   last = newnode;
}