My unsigned long long int return 0, help me

Asked Oct 05 '21 at 21:00

Active Oct 06 '21 at 03:52

Viewed 96 times

#include <stdio.h>

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

int main(void){
    unsigned long long int n;
    int t;
    scanf("%d", &t);
    for(int i = 0; i < t; i++){
        scanf("%lld", &n);
        long int a = factorial(n);
        printf("%lld\n", a);
    }
}

unsigned long long int factorial(unsigned long long int n){
    if(n == 0){
        return 1;
    }
    else{
        return (n * factorial(n - 1));
    }
}

I'm trying to print the factorial of 100, even using long long int it doesn't work, what am I doing wrong ?

edited Oct 05 '21 at 21:25

asked Oct 05 '21 at 21:00

Viana Viana

1

You're overflowing your data structure size. See [Which data type for calculating large factorials](https://stackoverflow.com/questions/15205587/which-data-type-or-data-structure-to-choose-to-calculate-factorial-of-100/15205645#15205645). – blackbrandt Oct 05 '21 at 21:02
1

`long int a` -> `long long int a` – tstanisl Oct 05 '21 at 21:04
2

try to use `double` instead of `long long int`. It should be large enough to handle `100!` but you may observe some small rounding errors (~1e-15 relative) – tstanisl Oct 05 '21 at 21:07
2

I have some doubts that it works up to 49! – M.M Oct 05 '21 at 21:15
2

`long long int` usually can represent integers up to `2^63-1`. Still much too small for `100!`. C doesn't have an integer type that can do it, so you'll need to start getting more creative. – Nate Eldredge Oct 05 '21 at 21:29
@tstanisl `double` is 8 byte under windows – Алексей Неудачин Oct 05 '21 at 21:31
@АлексейНеудачин `double` is 8-byte on all platforms that use IEEE-754 double precision – phuclv Oct 06 '21 at 04:16
https://stackoverflow.com/a/17039284 – Jonathon S. Oct 06 '21 at 11:23
regarding: `scanf("%lld", &n);` This should give a compiler message because `n` is UNSIGNED, Suggest: `scanf("%ulld", &n);` Notice the `u` for unsigned – user3629249 Oct 06 '21 at 20:50
regarding: `long int a = factorial(n);` the function: factorial()` returns a `unsigned long long int`, NOT a `long int` – user3629249 Oct 06 '21 at 20:54

My unsigned long long int return 0, help me

0 Answers0