Practice Exercise

Your task is to write a function, listSetDifference, that takes two lists, l1 and l2, that represent sets and returns a new list representing the set difference l1 - l2. The values in the returned list may be in any order. Since the given lists represent sets, you may assume that no value appears more than once in a list.

Assumptions and Constraints

• No value appears more than once in a list.
• You must not use arrays.
• You must not modify the given lists.

Download

While in your practice exercises directory, run the following command:

unzip /web/cs2521/practice-exercises/lists/listSetDifference/downloads/listSetDifference.zip

If you're working at home, download listSetDifference.zip by clicking on the above link and then unzip the downloaded file.

Files

list.c	Contains the implementation of basic list functions
list.h	Contains the definition of the list data structure and function prototypes
testListSetDifference.c	Contains the main function, which reads in two lists from standard input, calls listSetDifference, sorts the returned list, and prints out the result.
listSetDifference.c	Contains listSetDifference, the function you must implement
Makefile	A makefile to compile your code
tests/	A directory containing the inputs and expected outputs for some basic tests
autotest	A script that uses the tests in the tests directory to autotest your solution. You should only run this after you have tested your solution manually.

Examples

./testListSetDifference
Enter list 1: 4 3 1 7 6
Enter list 2: 6 2 1 5 3

Set 1: {4, 3, 1, 7, 6}
Set 2: {6, 2, 1, 5, 3}
Difference: {4, 7}

./testListSetDifference
Enter list 1: 1 3 5 7 9
Enter list 2: 8 6 4 2 0

Set 1: {1, 3, 5, 7, 9}
Set 2: {8, 6, 4, 2, 0}
Difference: {1, 3, 5, 7, 9}

./testListSetDifference
Enter list 1: 9 1 8 2 5
Enter list 2: 1 5 2 9 8

Set 1: {9, 1, 8, 2, 5}
Set 2: {1, 5, 2, 9, 8}
Difference: {}

Testing

You can compile and test your function using the following commands:

make                                     # compiles the program
./testListSetDifference                  # tests with manual input, outputs to terminal
./testListSetDifference < input-file     # tests with input from a file, outputs to terminal
./testListSetDifference < tests/01.in    # for example, tests with input from tests/01.in
                                           # (then manually compare with tests/01.exp)

After you have manually tested your solution, you can autotest it by running ./autotest. This will run some basic tests on your program, as well as check for memory leaks/errors.

It is possible to devise your own tests by creating your own input files. See the existing input files for examples. Note that you will need to check the output yourself.