求和

 

int main(){
    int n=100;
    double sum=0;
    for (int i = 1; i <=n ; ++i) {
       sum+=1.0/i;
    }
    printf("f(%d)=%f",n,sum);

}

int main(){
    int n=100;
    double sum=0;
    int sign=1;
    for (int i = 1; i <=n ; ++i) {
       sum+=sign*1.0/i;
       sign=-sign;
    }
    printf("f(%d)=%f",n,sum);

}