Ad hoc

0) Not fall into standard categories with well-studied solutions (Can't classify as other standard types).

1) Each one is different.

2) No specific or general techniques.

3) Fun, Each one present a new challenge!

4) Sometimes new data structures, unusual sets of loops/conditionals or rare special combinations. 

5) Careful reading!

6) Carefully sequencing the instructions given.

7) Reasonable optimization and a degree of analysis (E.g. avoid loops nested 5 deep).

8) More than other kinds!