Program received signal SIGSEGV.Segmentaation fault大一新生写一些很基础很基础的题目时遇到这个错误咋办？

Question

#include
int main()
{
int sum2(int n);
int n,y;
printf("Input an integer number\n");
scanf("%d",&n);
y=sum2(n);
printf("sum is %d\n",y);
return 0;
}
int sum2(int n)
{
int f;
if(n=0)
f=0;
else
f=n+sum2(n-1);
return(f);
}

Answer 1

#include
int sum2(int n);
int main()
{
int n,y;
printf("Input an integer number\n");
scanf("%d",&n);
y=sum2(n);
printf("sum is %d\n",y);
return 0;
}
int sum2(int n)
{
int f;
if(n=0)
f=0;
else
f=n+sum2(n-1);
return(f);
}