Week 10 Laboratory Exercises

Objectives

  • working with structs and pointers
  • introducing linked lists
  • using memory allocation

Activities To Be Completed

The following is a list of all the activities available to complete this week...

Worth 0.7 mark(s) in total:

  • mallocd_array
  • list_print
  • list_length
  • list_insert_head

Worth 0.7 mark(s) in total:

  • list_contains
  • list_insert_tail

Worth 0.4 mark(s) in total:

  • list_reverse

Problem sets are capped at 15 marks (there are 4 possible bonus marks from the three-dot exercises that can bring you up to a total of 15 if you missed out on any other marks in the one- or two-dot exercises).

Completing just the one and two-dot exercises every week can give you the full 15 marks needed in this component.

For more details, see the course outline.

Exercise
(●◌◌)
:

Working with malloc'd arrays

Download mallocd_array.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/mallocd_array/mallocd_array.c .

The main function has already been written for you. You must not modify it in any way.

Examples

dcc mallocd_array.c -o mallocd_array
./mallocd_array
Enter size: 5
Enter 5 integers:
1
2
3
4
5
The average of all values in the array is: 3.00
./mallocd_array
Enter size: 1
Enter 1 integers:
10
The average of all values in the array is: 10.00
./mallocd_array
Enter size: 3
Enter 3 integers:
5
-4
-3
The average of all values in the array is: -0.67

Assumptions/Restrictions/Clarifications

  • You do not need to handle memory leaks for this exercise. i.e. You should not call free
  • All inputs be of the correct type
New! You can run an automated code style checker using the following command:
1091 style mallocd_array.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest mallocd_array

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_mallocd_array mallocd_array.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise
(●◌◌)
:

Print out the elements of a Linked List

Download list_print.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/list_print/list_print.c .

Your task is to add code to this function in list_print.c:

// print a linked list in this format:
// 17 -> 34 -> 51 -> 68 -> X
void print(struct node *head) {

    // PUT YOUR CODE HERE
}

print is given one argument, head, which is the pointer to the first node in a linked list.

Your program will be supplied up to 50 integers, which will be put into a linked list that is passed to the print.

Add code to print so that it prints the elements in the list.

For example, if the linked list contains these 8 elements:

1, 7, 8, 9, 13, 19, 21, 42

print should print

1 -> 7 -> 8 -> 9 -> 13 -> 19 -> 21 -> 42 -> X

(including the X)

Testing

list_print.c also contains a main function which allows you to test your print function.

This main function:

  • converts the input from terminal into a linked list
  • assigns a pointer to the first node in the linked list to head
  • calls list_print(head)

Do not change this function. If you want to change it, you have misread the question.

Your list_print function will be called directly in marking. The main function is only to let you test your list_print function.

Examples

dcc list_print.c -o list_print
./list_print
1 2 4 8 16 32 64 128 256

1 -> 2 -> 4 -> 8 -> 16 -> 32 -> 64 -> 128 -> 256 -> X
./list_print
2 4 6 5 8 9

2 -> 4 -> 6 -> 5 -> 8 -> 9 -> X
./list_print
42 4

42 -> 4 -> X
./list_print
43

43 -> X
./list_print

X

Assumptions/Restrictions/Clarifications

  • You can assume the input will never be more than 50 integers.
  • print should not change the linked list it is given. Your function should not change the next or data fields of list nodes.
  • print should not use arrays.
  • print should not call malloc.
  • print should not call scanf (or getchar or fgets).
  • Do not change the supplied main function. It will not be tested or marked.
New! You can run an automated code style checker using the following command:
1091 style list_print.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest list_print

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_list_print list_print.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise
(●◌◌)
:

Find the length of a Linked List

Download list_length.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/list_length/list_length.c .

Your task is to add code to this function in list_length.c:

// Return the length of the linked list pointed by head
int length(struct node *head) {

    // PUT YOUR CODE HERE (change the next line!)
    return 42;

}

For this exercise, you will be given a linked list nodes containing integers, shown below.

struct node {
    struct node *next;
    int          data;
};

Your job is to complete the length function.

length is given one argument, head, which is the pointer to the first node in a linked list.

Add code to length so that its returns the length of the list.

For example if the linked list contains these 8 elements:

1, 7, 8, 9, 13, 19, 21, 42

length should return 8.

Testing

list_length.c also contains a main function which allows you to test your length function.

This main function:

  1. scans in number of items in the list, and its values; to create a linked list,
  2. assigns a pointer to the first node in the linked list to head,
  3. calls list_length(head), then
  4. prints the result.

Do not change this function. If you want to change it, you have misread the question.

Your list_length function will be called directly in marking. The main function is only to let you test your list_length function

Examples

dcc list_length.c -o list_length
./list_length 
How many numbers in initial list?: 9
1 2 3 6 5 4 9 9 0
Counted 9 elements in linked list.
./list_length
How many numbers in initial list?: 6
1 2 3 6 5 4
Counted 6 elements in linked list.
./list_length
How many numbers in initial list?: 5
1 2 3 4 5
Counted 5 elements in linked list.
./list_length 
How many numbers in initial list?: 2
42 4
Counted 2 elements in linked list.
./list_length
How many numbers in initial list?: 0
Counted 0 elements in linked list.

Assumptions/Restrictions/Clarifications

  • length should return a single integer
  • length should not change the linked list it is given
  • Your function should not change the next or data fields of list nodes
  • length should not use arrays
  • length should not call malloc
  • length should not call scanf (or getchar or fgets)
  • length should not print anything. It should not call printf
  • Do not change the supplied main function. It will not be tested or marked
New! You can run an automated code style checker using the following command:
1091 style list_length.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest list_length

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_list_length list_length.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise
(●◌◌)
:

Insert an element at the head of a Linked List

Download list_insert_head.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/list_insert_head/list_insert_head.c .

Your task is to add code to this function in list_insert_head.c:

// WRITE YOUR CODE INSIDE HERE ONLY!!!
// Insert a new node containing value at the start of the linked list.
// The head of the new list is returned.
struct node *insert_head(int value, struct node *head) {

    // PUT YOUR CODE HERE (change the next line!)
    return NULL;

}

insert_head is given two arguments, value and head.

  • value is an int
  • head is the pointer to the first node in a linked list

Add code to insert_head so that it creates a new list node (using malloc) containing value and places it at the start of the list.

insert_head should return a pointer to the new list.

For example if value is 12 and the linked list contains these 3 elements:

16, 7, 8

insert_head should return a pointer to a list with these elements:

12, 16, 7, 8

Testing

list_insert_head.c also contains a main function which allows you to test your insert_head function.

This main function:

  1. converts the first set of read integers to a linked list,
  2. assigns a pointer to the first node in the linked list to head
  3. reads another single integer from standard input and assigns it to value
  4. calls insert_head(value, head)
  5. prints the result.

Do not change this function. If you want to change it, you have misread the question.

Your insert_head function will be called directly in marking. The main function is only to let you test your insert_head function

dcc list_insert_head.c -o list_insert_head
./list_insert_head
How many numbers in initial list?: 
3
16 7 8
Enter number to insert to head: 
12
[12, 16, 7, 8]
./list_insert_head
How many numbers in initial list?: 
1
16
Enter number to insert to head: 
42
[42, 16]
./list_insert_head
How many numbers in initial list?: 
0
Enter number to insert to head: 
2
[2]

Assumptions/Restrictions/Clarifications

  • insert_head should not use arrays
  • insert_head should not call scanf (or getchar or fgets)
  • insert_head should not print anything. It should not call printf
  • Do not change the supplied main function. It will not be tested or marked
New! You can run an automated code style checker using the following command:
1091 style list_insert_head.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest list_insert_head

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_list_insert_head list_insert_head.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise
(●●◌)
:

Find an element in a Linked List

Download list_contains.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/list_contains/list_contains.c .

Your task is to add code to this function in list_contains.c:

// Return 1 if value occurs in linked list, 0 otherwise
int contains(char *value, struct node *head) {

    // PUT YOUR CODE HERE (change the next line!)
    return 42;
}

contains is given two arguments, a string value and head which is the pointer to the first node in a linked list.

Add code to contains so that it returns 1 if value occurs in the linked list and otherwise it returns 0.

For example if the linked list contains these 7 elements:

"mozzarella" "pepperoni" "basil" "ham" "tomato bacon" "cheesy-crust" "bocconcini"

and contains is called with value of "mozzarella",

contains should return 1.

Testing

list_contains.c also contains a main function which allows you to test your contains function.

This main function:

  1. Asks for how many strings will be in our list,
  2. reads in and converts that n many strings to a linked list,
  3. assigns a pointer to the first node in the linked list to head,
  4. reads another single string from standard input and assigns it to value.
  5. calls list_contains(value, head) and
  6. prints the result.

Do not change this function. If you want to change it, you have misread the question.

Your list_contains function will be called directly in marking. The main function is only to let you test your list_contains function

Examples

dcc list_contains.c -o list_contains
./list_contains
How many strings in initial list?: 4
pepperoni
ham
basil
capsicum
Enter word to check contained: basil
1
./list_contains
How many strings in initial list?: 4
pepperoni
ham
basil
capsicum
Enter word to check contained: mozzarella
0
./list_contains 
How many strings in initial list?: 4
chicken
mushroom
mushroom
pizza-sauce
Enter word to check contained: mushroom
1
./list_contains
How many strings in initial list?: 4
tomato
bacon
capsicum
mushroom
Enter word to check contained: pepperoni
0
./list_contains
How many strings in initial list?: 0
Enter word to check contained: tomato
0

Assumptions/Restrictions/Clarifications

  • String matching is case sensitive. "Tomato" does not match "tomato". No strings will have the space character in them
  • contains should return a single integer.
  • contains should not change the linked list it is given. Your function should not change the next or data fields of list nodes.
  • contains should not use arrays.
  • contains should not call malloc.
  • contains should not call scanf (or getchar or fgets).
  • contains should not print anything. It should not call printf.
  • Do not change the supplied main function. It will not be tested or marked.
New! You can run an automated code style checker using the following command:
1091 style list_contains.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest list_contains

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_list_contains list_contains.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise
(●●◌)
:

Insert an element at the end of a Linked List

Download list_insert_tail.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/list_insert_tail/list_insert_tail.c .

Your task is to add code to this function in list_insert_tail.c:

// Insert a new node containing value at the end of the linked list.
// Parameters:
//      `int value`         : The value to insert.
//      `struct list *list` : a struct * containing the head pointer of the 
//      linked list.
void insert_tail(int value, struct list *list) {
    // PUT YOUR CODE HERE
}

insert_tail is given two arguments:

  • value is an int
  • list is the pointer to a struct list which contains
  • the head (a pointer to the first node) of the linked list

Add code to insert_tail so that it creates a new list node (using malloc) containing value and places it at the end of the list.

insert_tail should return nothing.

For example if value is 12 and the linked list contains these 3 elements:

16, 7, 8

insert_tail should modify the linked list so that it now has these elements:

16, 7, 8, 12

Testing

list_insert_tail.c also contains a main function which allows you to test your insert_tail function.

This main function:

  1. Asks for the size of the initial linked list
  2. converts the first set of scanned inputs to a linked list
  3. stores the first node of the linked list in a struct list.
  4. reads a single integer from standard input and assigns it to value
  5. calls insert_tail(value, list)
  6. prints the result.

Do not change this main function. If you want to change it, you have misread the question.

Your insert_tail function will be called directly in marking. The main function is only to let you test your insert_tail function

Examples

dcc list_insert_tail.c -o list_insert_tail
./list_insert_tail
How many numbers in initial list?: 3
16 7 8
Enter value to insert: 12
[16, 7, 8, 12]
./list_insert_tail
How many numbers in initial list?: 1
16
Enter value to insert: 42
[16, 42]
./list_insert_tail
How many numbers in initial list?: 0
Enter value to insert: 2
[2]

Assumptions/Restrictions/Clarifications

  • insert_tail should not use arrays
  • insert_tail should not call scanf (or getchar or fgets)
  • insert_tail should not print anything. It should not call printf
  • Do not change the supplied main function. It will not be tested or marked
New! You can run an automated code style checker using the following command:
1091 style list_insert_tail.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest list_insert_tail

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_list_insert_tail list_insert_tail.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise
(●●●)
:

Reverse a Linked List

Download list_reverse.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/list_reverse/list_reverse.c .

Your task is to add code to this function in list_reverse.c:

//
// Place the list pointed to by head into reverse order.
// The head of the list is returned.
//
struct node *reverse(struct node *head) {

    // PUT YOUR CODE HERE (change the next line!)
    return NULL;

}

Note list_reverse.c uses the following familiar data type:

struct node {
    struct node *next;
    int          data;
};

list_reverse is given one argument, head which is the pointer to the first node in the linked list.

Add code to reverse which rearranges the list to be in reverse order.

reverse should return a pointer to the new list.

reverse must rearrange the list by changing the next fields of nodes.

reverse must not change the data fields of nodes.

For example if the linked list contains these 8 elements:

16, 7, 8, 12, 13, 19, 21, 12

reverse should return a pointer to a list with these elements:

12, 21, 19, 13, 12, 8, 7, 16

Testing

list_reverse.c also contains a main function which allows you to test your list_reverse function.

This main function:

  • takes in the size of the linked list,
  • converts the input numbers to a linked list,
  • assigns a pointer to the first node in the linked list to head,
  • calls reverse(head) and
  • prints the result.

Do not change this function. If you want to change it, you have misread the question.

Your list_reverse function will be called directly in marking. The main function is only to let you test your list_reverse function

Examples

dcc list_reverse.c -o list_reverse
./list_reverse
How many numbers in list?: 8
16 7 8 12 13 19 21 12
[12, 21, 19, 13, 12, 8, 7, 16]
./list_reverse
How many numbers in list?: 6
2 4 6 2 4 6
[6, 4, 2, 6, 4, 2]
./list_reverse 42
How many numbers in list?: 1
42
[42]
./list_reverse
How many numbers in list?: 0
[]

Assumptions/Restrictions/Clarifications

  • list_reverse should not change the data fields of list nodes
  • list_reverse should not use arrays
  • list_reverse should not call malloc
  • list_reverse should not call scanf (or getchar or fgets)
  • list_reverse should not print anything. It should not call printf
  • Do not change the supplied main function. It will not be tested or marked
New! You can run an automated code style checker using the following command:
1091 style list_reverse.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest list_reverse

When you are finished working on this exercise, you must submit your work by running give:

give dp1091 lab10_list_reverse list_reverse.c
    

You must run give before Monday 04 November 09:00 to obtain the marks for this lab exercise. Note that this is an individual exercise, the work you submit with give must be entirely your own.

Exercise — individual:
(Not For Marks) Debugging - Product

Copy the program debug_product.c from the course account to your directory by typing (make sure you type the dot at the end):

cp ~dp1091/public_html/24T3/activities/debug_product/debug_product.c .

Note that this exercise is not marked or worth marks!

Debugging Tips!

Some debugging tips for you:

  • dcc output - as you run into issues, dcc will point you to where the errors are. Remember that dcc gives you the line number the issue is on, and will give some sort of explanation. Make sure you read everything dcc gives you. Sometimes we get “errors carried forward”, so find your first error, fix that, then recompile.
  • print statements - sometimes it can be handy to see if the flow of your code puts you in the spot you expect it to be (ie. inside the right if statement, or going through a loop the correct amount of times). A quick way you can check this is by putting print statements in your code for testing purposes, like "the value of x is %d and y is %d". This lets you check that you got against what you expected.
  • DPST1091 debugging guide - https://cgi.cse.unsw.edu.au/~dp1091/23T3/resources/debugging_guide.html

The Task

This exercise takes integers as command line arguments and calculates their cumulative product. However, if the number is 0 or not an integer, it is not added to the cumulative product of command line arguments. Currently it has some issues - it is your job to figure them out and fix the code.

Examples

dcc debug_product.c -o debug_product
./debug_product 0 1 2 3 4 5
Product: 120
./debug_product -5 1 -1 -2
Product: -10
./debug_product 100 these are my arguments -2
Product: -200
./debug_product these are my command line arguments
Product: 0

Assumptions/Restrictions/Clarifications

  • You may find the atoi() function in the C standard library (stdlib.h) useful.
  • You may assume that argv[0] will always be the program name.
New! You can run an automated code style checker using the following command:
1091 style debug_product.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest debug_product

Exercise — individual:
(Not For Marks) Debugging - List insert second last

Copy the program debug_insert_second_last.c from the course account to your directory by typing (make sure you type the dot at the end):

cp ~dp1091/public_html/24T3/activities/debug_insert_second_last/debug_insert_second_last.c .

Note that this exercise is not marked or worth marks!

Debugging Tips!

Some debugging tips for you:

  • dcc output - as you run into issues, dcc will point you to where the errors are. Remember that dcc gives you the line number the issue is on, and will give some sort of explanation. Make sure you read everything dcc gives you. Sometimes we get “errors carried forward”, so find your first error, fix that, then recompile.
  • print statements - sometimes it can be handy to see if the flow of your code puts you in the spot you expect it to be (ie. inside the right if statement, or going through a loop the correct amount of times). A quick way you can check this is by putting print statements in your code for testing purposes, like "the value of x is %d and y is %d". This lets you check that you got against what you expected.
  • DPST1091 debugging guide - https://cgi.cse.unsw.edu.au/~dp1091/23T3/resources/debugging_guide.html

The Task

This exercise takes in the length of a linked list, followed by the elements of the list. Then it takes in a single value to be inserted as the second last node of the list previously created.

For example if the existing list is 1 -> 2 -> 3 -> X and a node with value 4 is being inserted, after insertion the list is as follows: 1 -> 2 -> 4 -> 3 -> X. Note, the node containging the value 4 is inserted before the node containing the value 3 since the node containing the value 3 is at the tail (i.e the last node) of the list since it points at null.

Currently it has some issues when attempting to insert the value as the second last node in the list - it is your job to figure them out and fix the code.

Examples

dcc debug_insert_second_last.c -o debug_insert_second_last
./debug_insert_second_last
How many numbers in initial list?: 3
1 2 3
Enter the value to insert: 4
[1, 2, 4, 3]
./debug_insert_second_last
How many numbers in initial list?: 6
5 2 9 10 4 7
Enter the value to insert: 0
[5, 2, 9, 10, 4, 0, 7]
./debug_insert_second_last
How many numbers in initial list?: 1
23
Enter the value to insert: 5
[5, 23]
./debug_insert_second_last
How many numbers in initial list?: 0
Enter the value to insert: 4
[4]

Assumptions/Restrictions/Clarifications

  • You do not need to edit the main(), array_to_list(), print_list() or get_list_length() functions.
New! You can run an automated code style checker using the following command:
1091 style debug_insert_second_last.c
    

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest debug_insert_second_last

Submission

When you are finished each exercises make sure you submit your work by running give.

You only need to do this if the exercise specifies a give command, otherwise - the exercise is not worth marks.

You can run give multiple times. Only your last submission will be marked.

Don't submit any exercises you haven't attempted.

If you are working at home, you may find it more convenient to upload your work via give's web interface.

Remember you have until Week 11 Monday 9:00am to submit your work.

You cannot obtain marks by e-mailing your code to tutors or lecturers.

You check the files you have submitted here.

Automarking will be run by the lecturer several days after the submission deadline, using test cases different to those autotest runs for you. (Hint: do your own testing as well as running autotest.)

After automarking is run by the lecturer you can view your results here. The resulting mark will also be available via give's web interface.

Lab Marks

When all components of a lab are automarked you should be able to view the the marks via give's web interface or by running this command on a CSE machine:

1091 classrun -sturec

Generative AI Permission Level

In completing this assessment, you are permitted to use standard editing and referencing functions in the software you use to complete your assessment. These functions are described below. You must not use any functions that generate or paraphrase passages of text or other media, whether based on your own work or not.

If your Convenor has concerns that your submission contains passages of AI-generated text or media, you may be asked to account for your work. If you are unable to satisfactorily demonstrate your understanding of your submission, you may be referred to UNSW Conduct & Integrity Office for investigation for academic misconduct and possible penalties.

DPST1091/CPTG1391 Specific Information

You are permitted to use the tools dcc-help to help you understand the error messages you may get when compiling the code you have written.

You are permitted to use autotest-help to help you understand why your code may not be passing the automated tests.

You are not permitted to submit code generated by automatic AI tools such as Github Copilot, ChatGPT, Google Bard in DPST1091/CPTG1391/COMP1511 for assignments. Submitting code generated by Github Copilot, ChatGPT, Google Bard and similar tools will be treated as plagiarism.

Our reasoning behind our decisions:

Systems such as Github Copilot and ChatGPT based on large language models or other generative artificial intelligence techniques, look likely to become heavily used by programmers. However, you need a good understanding of the language you are coding in and the systems involved before you can effectively use these tools. Using these tools to generate code for DPST1091/CPTG1391/COMP1511 instead of writing the code yourself will hinder your learning.