This is the second part of two assignments. This part asks you to
shuffle a deck of cards multiple times.
Learning Goals
==============
* Use recursion to solve a problem.
* Understand how to modify a program (you wrote) for a slightly different problem
WHAT TO SUBMIT
==============
```
zip hw12.zip shuffle.c
```
Upload `hw12.zip`.
Count Unique Outputs
====================
The previous assignment tells you to use `sort` to order outputs so
that they can be compared. You can extend this further by going
through multiple programs. After `sort`, you can use `uniq` to keep
only unique lines.
`./hw11 4 2 | sort | uniq`
gives you the unique lines. You need to use `sort` before `uniq`
because `uniq` merge agencent identical lines. If two identical lines
are not adjacent, `uniq` does not merge them.
You can add `wc` to count the number of lines.
`./hw11 6 2 | sort | uniq | wc`
tells you how many unique lines are generated.
Check how many unique orders ./hw11 8 2 can generate. Do they cover
all possible orders of 8 cards?
Why is there no `ifdef` and `endif` in shuffle.c?
=================================================
This assignment requires only one function `shuffle`. Thus, there is
no need using `ifdef` and `endif`. It is likely that you need to add
additional functions called by `shuffle`.
