c语音基础题，满满的求知欲

Question

Answer 1

#include <stdio.h>
int fun(int n){
    int i = 0;
    int flag = 1; //存返回值
    if (0 == n || 1 == n){
        return 1;
    }else{
        for (i = 2; i <= n; i++){
            flag *= i;
        }
        return flag;
    }
}
double sum(int n){//求和函数
    int i;                      
    double sum = 0;
    for (i = 1; i <= n; i++){
        sum += 1.0 / fun(i);
    }
    return sum;
}
void main(){
    int n;                 
    printf("请输入项数");
    scanf("%d",&n);
    printf("sum = %lf", sum(n));
}