Cash

Problem to Solve

In a file called cash.py in a folder called sentimental-cash, write a program that asks the user how much change is owed and then spits out the minimum number of coins with which said change can be made. You can do this exactly as you did in Problem Set 1, except that your program this time should be written in Python, and you should assume that the user will input their change in dollars (e.g., 0.50 dollars instead of 50 cents).

Demo

Specification

Use get_float from the CS50 Library to get the user’s input and print to output your answer. Assume that the only coins available are quarters (25¢), dimes (10¢), nickels (5¢), and pennies (1¢).
- We ask that you use get_float so that you can handle dollars and cents, albeit sans dollar sign. In other words, if some customer is owed $9.75 (as in the case where a newspaper costs 25¢ but the customer pays with a $10 bill), assume that your program’s input will be 9.75 and not $9.75 or 975. However, if some customer is owed $9 exactly, assume that your program’s input will be 9.00 or just 9 but, again, not $9 or 900. Of course, by nature of floating-point values, your program will likely work with inputs like 9.0 and 9.000 as well; you need not worry about checking whether the user’s input is “formatted” like money should be.
If the user fails to provide a non-negative value, your program should re-prompt the user for a valid amount again and again until the user complies.
Incidentally, so that we can automate some tests of your code, we ask that your program’s last line of output be only the minimum number of coins possible: an integer followed by a newline.

How to Test

While check50 is available for this problem, you’re encouraged to first test your code on your own for each of the following.

Run your program as python cash.py, and wait for a prompt for input. Type in 0.41 and press enter. Your program should output 4.
Run your program as python cash.py, and wait for a prompt for input. Type in 0.01 and press enter. Your program should output 1.
Run your program as python cash.py, and wait for a prompt for input. Type in 0.15 and press enter. Your program should output 2.
Run your program as python cash.py, and wait for a prompt for input. Type in 1.60 and press enter. Your program should output 7.
Run your program as python cash.py, and wait for a prompt for input. Type in 23 and press enter. Your program should output 92.
Run your program as python cash.py, and wait for a prompt for input. Type in 4.2 and press enter. Your program should output 18.
Run your program as python cash.py, and wait for a prompt for input. Type in -1 and press enter. Your program should reject this input as invalid, as by re-prompting the user to type in another number.
Run your program as python cash.py, and wait for a prompt for input. Type in foo and press enter. Your program should reject this input as invalid, as by re-prompting the user to type in another number.
Run your program as python cash.py, and wait for a prompt for input. Do not type anything, and press enter. Your program should reject this input as invalid, as by re-prompting the user to type in another number.

Correctness

check50 cs50/problems/2024/spring/sentimental/cash

Style

style50 cash.py

How to Submit

Per Step 4 below, after you submit, be sure to check your autograder results. If you see SUBMISSION ERROR: missing files (0.0/1.0), it means your file was not named exactly as prescribed (or you uploaded it to the wrong problem).

Correctness in submissions entails everything from reading the specification, writing code that is compliant with it, and submitting files with the correct name. If you see this error, you should resubmit right away, making sure your submission is fully compliant with the specification. The staff will not adjust your filenames for you after the fact!

Download your cash.py file by control-clicking or right-clicking on the file in your codespace’s file browser and choosing Download.
Go to CS50’s Gradescope page.
Click Problem Set 6: Sentimental (Cash).
Drag and drop your cash.py file to the area that says Drag & Drop. Be sure it has that exact filename! If you upload a file with a different name, the autograder likely will fail when trying to run it. Ensuring you have uploaded files with the correct filename is your responsibility!
Click Upload.

You should see a message that says “Problem Set 6: Sentimental (Cash) submitted successfully!”