Assignment 3: If you malloc something, set it free
Due Friday, February 7th, before midnight
The goals for this assignment are:
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Work with pointers
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Work with malloc/free
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Work with arrays
1. Update your repository
Do a fetch upstream to obtain the basecode for this assignment.
Using the command line
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Open terminal and change your current directory to your assignment repository.
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Run the command
git fetch upstream -
Run the command
git merge upstream/main
Your repository should now contain a new folder named A03.
The fetch and merge commands update your repository with any changes from the original.
2. Repeat! Repeat! Repeat!
Implement a program, repeat.c, that asks the user for a string s and an integer n and
then creates a new string that repeats s n times. For example, if the user inputs "ha" and
the number 3, the program creates a string "hahaha".
$ make repeat
gcc repeat.c -o repeat
$ ./repeat
Enter a word: ha
Enter a count: 3
Your word is hahaha
$ ./repeat
Enter a word: ha
Enter a count: 1000
hahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahaha
hahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahaha
hahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahaha
hahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahaha
hahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahaha
hahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahahaha
[truncated]
$ ./repeat
Enter a word: hi
Enter a count: 1000000000000
Cannot allocate new string. Exiting...Requirements/Hints:
* Your program can assume that the user enters words that are smaller than 32 characters.
* Your program should use malloc and free.
* Your program should check that malloc is successful.
3. Dynamic snackbar
Implement a program, dynamic_snackbar.c, that allows users to add snacks to the snackbar.
Unlike last week’s snackbar, your program only needs two features:
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The ability to add a new snack to the list of snacks
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The ability to print out the current list of snacks
$ make dynamic_snackbar
gcc dynamic_snackbar.c -o dynamic_snackbar
$ ./dynamic_snackbar
Enter a number of snacks: 3
Enter a name: Slurm
Enter a cost: 1.50
Enter a quantity: 3
Enter a name: Beans
Enter a cost: 5
Enter a quantity: 1
Enter a name: Carrots
Enter a cost: 2
Enter a quantity: 10
Welcome to Dynamic Donna's Snack Bar.
0) Slurm cost: $1.50 quantity: 3
1) Beans cost: $5.00 quantity: 1
2) Carrots cost: $2.00 quantity: 10Requirements/Hints:
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You must use malloc to create an array large enough to hold all the snacks
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Use scanf to get the number of snacks and their attributes
| You do not need to type in the attributes every time. You can put the inputs in a file and then use redirection to load it. |
4. Wampus
In the file, wampus.c, implement a program that randomly places a Wampus within a NxM grid.
Then, fill in the remaining cells with their distance from the Wampus (using the Manhattan distance).
$ ./wampus
Number of rows: 2
Number of columns: 3
3 2 1
2 1 W
$ ./wampus
Number of rows: 1
Number of columns: 1
W
$ ./wampus
Number of rows: 3
Number of columns: 4
1 W 1 2
2 1 2 3
3 2 3 4
$ ./wampus
Number of rows: 6
Number of columns: 3
1 W 1
2 1 2
3 2 3
4 3 4
5 4 5
6 5 6Requirements/Hints:
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Use rand() to generate a cell (i,j) for the Wampus.
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Set a seed so that rand() produces different boards each time.
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Your program should ask the user for a width and height for the grid
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Your program should print the grid with its values
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Your program should use malloc/free to create the grid
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You can assume that the user will only enter positive values for rows and columns
5. Grading Rubric
Assignment rubrics
Grades are out of 4 points.
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(1 point) repeat
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(0.1 points) style and header comment
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(0.5 points) no memory errors
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(0.4 points) correct behavior: asks the user for input and creates the new string
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(1 point) wampus
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(0.1 points) style and header comment
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(0.5 points) no memory errors
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(0.4 points) correct behavior: uses a command line argument to get the size and outputs the correct board
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(2 points) dynamic snackbar
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(0.15 points) style and header comment
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(0.05 points) defines a struct to hold the information for each snack
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(0.8 points) correctly loads data and prints results in a table
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(1 points) creates an array using malloc to hold the data from the file (No memory errors)
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Code rubrics
For full credit, your C programs must be feature-complete, robust (e.g. run without memory errors or crashing) and have good style.
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Some credit lost for missing features or bugs, depending on severity of error
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-5% for style errors. See the class coding style here.
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-50% for memory errors
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-100% for failure to checkin work to Github
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-100% for failure to compile on linux using make