SPOJ -Small factorials

Question

http://www.spoj.com/problems/FCTRL2/
My code is showing compilation error in Spoj,although running accurate in my compiler.
**IDE - Codeblocks **

int cal(int );


int main()
{
  int i,t;
  int n[100];
  scanf("%d",&t);
   for(i=0;i<t;i++)
    {
       scanf("%d",&n[i]);
    }

for(i=0;i<t;i++)
{
  printf("%d",cal(n[i]));
  printf("\n");
}
return 0;
}
int cal(int x)
{
  int j,a=1;
 for(j=x;j>=1;j--)
 {
 a=a*j;


 }
 return a;


}

A simple q: what if input for `t` greater than `100`? Also, please indent your code properly. Can you please post the `error`s too? — Sourav Ghosh, Jan 10 '15 at 09:47
You must be able to compute `100!`, but can not be represented in your use simple `int`. — BLUEPIXY, Jan 10 '15 at 09:48
it is not enough even `long int`. You need to implement a simple multiple length arithmetic. — BLUEPIXY, Jan 10 '15 at 09:59
100! = 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000 — BLUEPIXY, Jan 10 '15 at 10:02
http://stackoverflow.com/a/17039284/971127 you customize(change cell size and without malloc & realloc) it for your problem. — BLUEPIXY, Jan 10 '15 at 10:07

score 2 · Answer 1 · answered Jan 10 '15 at 09:48

2

printf and scanf are not defined. You need to include the stdio library.

I get this error locally:

test.c: In function ‘main’:
test.c:8:9: warning: incompatible implicit declaration of built-in function ‘scanf’
         scanf("%d",&t);
         ^
test.c:16:16: warning: incompatible implicit declaration of built-in function ‘printf’
                printf("%d",cal(n[i]));
                ^

answered Jan 10 '15 at 09:48

mirelon

4,896
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Really do you think this is the issue? – Gopi Jan 10 '15 at 09:49
@Gopi Maybe not, but you never know !!. :-) Let's wait for OP to post his/her _error_ (s). – Sourav Ghosh Jan 10 '15 at 09:50
WELL I have not included the header files intentionally and yes "data type" is the error. – Beginner Jan 10 '15 at 09:54

score 0 · Answer 2 · answered Aug 03 '15 at 15:50

For every integer input you have to calculate the factorial. This is very simple in languages like python or java which have built-in support for big integer types. Although it gives tough time for people using C / C++ or languages that do not have a built-in biginteger type.

Now, the maximum number that can be stored in an unsigned 32 bit integer is 2 ^ 32 – 1 and in an unsigned 64 bit integer is 2 ^ 64 – 1. Something like 100! has over 150 decimal digits. The data types mentioned earlier can store numbers having at most 9 and 19 decimal digits respectively. So, you need to find a way to store the 150+ digits that we will get as the answer. Think of using arrays to store each decimals.

SPOJ -Small factorials

2 Answers2

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