C program to find the trailing ZEROS at the end of a FACTORIAL of a given number

Question

I have return the code to find a factorial and to display trailing zeros at the end of the factorial, but the output is wrong... could you please help me to find the mistake?

#include <stdio.h>

int main() {
    int m = 1, i, N, count = 0;

    scanf("%d", &N);

    for (i = 1; i <= N; i++) {
        m = m * i;
    }
    printf("%d", m);

    while (m > 0) {
        if ((m % 10) == 0) {
            count = count + 1;
            m = m / 10;
        }
        break;
    }
    printf("%d", count);

    return 0;
}

Answer 1

you have two problems

• your collapse the two outputs so you see only one of them / you cannot see who is who, just add a separator between them
• an else is missing when you count so you count to only up to 1 and the result is wrong from factorial 10

So the minimal changes produce :

int main()
{
    int m=1,i,N,count=0;

    scanf("%d",&N);

    for(i=1;i<=N;i++)
    {
        m=m*i;
    }
    printf("%d\n",m); /* <<< added \n */

    while(m>0)
    {
      if((m%10)==0)
      {
        count=count+1;
        m=m/10;
      }
      else /* <<< added else */
        break;
    }
    printf("%d\n",count); /* <<< added \n */

    return 0;
}

after the changes :

pi@raspberrypi:/tmp $ ./a.out
5
120
1
pi@raspberrypi:/tmp $ ./a.out
10
3628800
2

Of course that supposes first you are able to compute the factorial without overflow

I also encourage you to check a value was read by scanf, checking it returns 1