1.
Voraussetzung

p -----> NULL

         +--------+
r -----> |  1     |
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  2     |
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 12

         +--------+
r -----> |  1     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  2     |
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 13

         +--------+
         |  1     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
r -----> |  2     |
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 14 ( p = NULL )

         +--------+
         |  1     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

         +--------+
r -----> |  2     |
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 15

         +--------+
p -----> |  1     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

         +--------+
r -----> |  2     |
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 11 ( r != 0) also nochmals

Linie 12 die zweite

         +--------+
p -----> |  1     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

         +--------+
r -----> |  2     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
         |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 13 die zweite

         +--------+
p -----> |  1     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

         +--------+
         |  2     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
         +--------+
r -----> |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 14 die zweite

         +--------+
p -----> |  1     | <---------+
         +--------+           |
         | next + |           |
         +------+-+           |
                |             |
                v             |
              NULL            |
                              |
         +--------+           |
         |  2     | <----- q  |
         +--------+           |
         | next + +-----------+
         +--------+
                
                
         +--------+
r -----> |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 15 die zweite

         +--------+
         |  1     | <---------+
         +--------+           |
         | next + |           |
         +------+-+           |
                |             |
                v             |
              NULL            |
                              |
         +--------+           |
p -----> |  2     | <----- q  |
         +--------+           |
         | next + +-----------+
         +--------+
                
                
         +--------+
r -----> |  3     |
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 11 ( r != 0) also nochmals

Linie 12 die dritte

         +--------+
         |  1     | <---------+
         +--------+           |
         | next + |           |
         +------+-+           |
                |             |
                v             |
              NULL            |
                              |
         +--------+           |
p -----> |  2     |           |
         +--------+           |
         | next + +-----------+
         +--------+
                
                
         +--------+
r -----> |  3     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
              NULL

Linie 13 die dritte

         +--------+
         |  1     | <---------+
         +--------+           |
         | next + |           |
         +------+-+           |
                |             |
                v             |
              NULL            |
                              |
         +--------+           |
p -----> |  2     |           |
         +--------+           |
         | next + +-----------+
         +--------+
                
                
         +--------+
         |  3     | <----- q
         +--------+
         | next + |
         +------+-+
                |
                v
r ----------> NULL

Linie 14 die dritte

         +--------+
         |  1     | <---------+
         +--------+           |
         | next + |           |
         +------+-+           |
                |             |
                v             |
              NULL            |
                              |
         +--------+           |
p -----> |  2     | <---------|---+
         +--------+           |   |
         | next + +-----------+   |
         +--------+               |
                                  |
                                  |
         +--------+               |
         |  3     | <----- q      |
         +--------+               |
         | next + +---------------+
         +--------+

r ----------> NULL

Linie 15 die dritte

         +--------+
         |  1     | <---------+
         +--------+           |
         | next + |           |
         +------+-+           |
                |             |
                v             |
              NULL            |
                              |
         +--------+           |
         |  2     | <---------|---+
         +--------+           |   |
         | next + +-----------+   |
         +--------+               |
                                  |
                                  |
         +--------+               |
p -----> |  3     | <----- q      |
         +--------+               |
         | next + +---------------+
         +--------+

r ----------> NULL

Linie 11 da ( r = 0 ) keinen weiteren durchgang

Linie 17

         +--------+
p -----> |  3     |
         +--------+
         | next + +
         +--------+

p wird zurück gegeben.


2.
Die Funktion gibt einen Zeiger auf das vor dem Aufruf der Funktion letzte
Element der verketteten Liste zurück. Dieses Element ist nun das erste
Element in der Liste (-> Headpointer).
Die Liste liegt nun in umgekehrter Reihenfolge vor.