Understanding a factorial function assignment

Question

I have a problem understanding what this means:

"Write a function calculating the factorial of a number using the largest possible, appropriate return type. This function will have one parameter, and will return the factorial of that number. The program needs to stop working when the numbers get too large to fit in your variables. Test your function by calling it from main(). Call the function in a loop, and output the results like this:"

Factorials:

1: 1
2: 2
3: 6
4: 24
5: 120
… etc.

It seems clear enough to me. What are you having trouble with? — , Dec 15 '13 at 04:51
http://stackoverflow.com/questions/199333/best-way-to-detect-integer-overflow-in-c-c — Kaustav Ray, Dec 15 '13 at 04:51
I think I;m having trouble with the output. I can get, let's say the factorial of an integer and display the final result. But I'm not sure how to output the result each time a factorial is calculated. I also don't know how to let the program run till it reaches the maximum of the data range. I'm using an unsigned long long int for that. — user3101059, Dec 15 '13 at 04:57
@Bit Fiddling Code Monkey the math part of it is not the problem — user3101059, Dec 15 '13 at 04:58
fact * next_value is overflow? when `ULLONG_MAX / next_value < fact` — BLUEPIXY, Dec 15 '13 at 05:04

score 0 · Accepted Answer · answered Dec 15 '13 at 05:05

In a loop, calculate the factorial for a given n. For each iteration, use printf to show the current state of your factorial calculation. Choose a return type that can hold the largest possible factorial. If a calculation will get too large, and cause an overflow, cap the calculation at the previous value.

The stub of your calculate factorial function will be something like this:

unsigned long long calculateFactorial(int n)
{
    unsigned long long factorial;

    /* Create a loop to calculate the factorial of n. */
    /* Print the progress of your calculation using   */
    /* %llu as your printf format specifier.          */

    return factorial;
}

@user3101059 Ask for more help if you need it. Also, I you think I answered your question, how about you toss me a bone and click the check mark on this answer so I can get a reputation boost. :-D — Fiddling Bits, Dec 15 '13 at 05:09

Understanding a factorial function assignment

1 Answers1