C Programming question about power, factorial, and combination

Question

I have been assigned a question about solving an equation with power factorial and combination. In this question, I was assigned to code power and factorial with a for loop. And I think I have done that (they are working one by one). Also in the main function, I need to calculate an equation. So here is my code, it looks right to me. but eventually I am getting a "Floating point exception (core dumped)" error. Any help can be nice, I actually don't want the right answer, if you can explain why am I getting this error, that would be helpful. Thank you. (I cannot upload a photo because of reputation things if there is a way to share photo I will.)

#include <stdio.h>

int factorial(int n){
    int i,result=1;
    for(i=1; i<=n; ++i){
        result = result*i;
    }
    return result;
}

int power(int x,int y){ // base -> x , exponent -> y
    int result=1;
    for(int i=1;i<=y;i++) // multiply x, y times
        result*=x;
    return result;
}

int combination(int n,int r){
    return factorial(n)/(factorial(r)*factorial(n-r));
}

int main()
{
    double ans=0;
    int n;
    printf("Enter n : ");
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        int denominator = 0,numerator = 0; // set denominator, numerator to 0 because we are going to add to them
        for(int z=1;z<=n-i;z++)
            numerator += power(i,z);
        
        for(int j=1;j<=i;j++)
            denominator += ((power(j,n)*combination(n,j))/factorial(n));
        
        ans = ans + (numerator/denominator);
    }
    printf("Resut is : %f",ans);
    return 0;
}

Answer 1

If you are sure you want to perform integer arithmetic, you need to ensure the denominator is not zero before the division:

if (denominator != 0)
    ans = ans + (numerator/denominator);

In the first iteration of the outer for loop, i=1 , which means the denominator loop will execute only once, setting the denominator to: 1^n * C(n 1) / n! = 1/(n-1)! 1^n * C(n 1) / n! = 1/(n-1)! , which is 0 in integer division (unless n=1 or n=2 ).

If you did not intend to perform integer arithmetic, then change the type of the denominator to double :

double denominator = 0, numerator = 0;