|
|
|
|
|
|
|
At this point, you are ready to learn about an
implementation of lists using external pointers. This implementation
involves not only a link class, but also a
header class. Each header object,
one per list, contains a pointer to the first link
object. If the list is empty, the link pointer is the
null pointer, as in the following illustration:
*-------* A header object | | |-------| | 0 | A null pointer to first link object *-------*
The following illustration shows a list that contains three cars:
*-------* A header object
| |
|-------|
| |
*-------*
|
v
*-------* *-------* *-------* Three link objects
| | ----> | | ----> | 0 |
|-------| |-------| |-------|
| | | | | |
*-------* *-------* *-------*
| | |
v v v
*-------* *-------* *-------* Three railroad_car objects
| | | | | |
|-------| |-------| |-------|
| | | | | |