C++实验报告1

习题2-1

#include <stdio.h>
int main(){
    int sum=1;
    for(int i=1;i<=5;i++) sum*=i;
    printf("%d\n",sum);
    return 0;
}

习题2-3

#include <stdio.h>
int main(){
    for(int year=2000;year<2500;year++){
        if(year%400==0||(year%4==0&&year%100)) 
            printf("%d年是闰年\n",year);
        else printf("%d年不是闰年\n",year);
    }
    return 0;
}

习题2-4

#include <stdio.h>
int main(){
    double ans=0;
    for(double i=1;i<=99;i+=2){
        ans+=1/i-1/(i+1);
    }
    printf("%lf\n",ans);
    return 0;
}

习题2-5

#include <stdio.h>
#include <math.h>
int main(){
    int a,b;
    scanf("%d",&a);
    b=sqrt(a+0.5);
    for(int i=2;i<=b;i++)
        if(a%i==0){
            printf("不是素数");
            return 0;
        } 
    printf("是素数");
    return 0;
    return 0;
}

附加题1

#include <stdio.h>
int main(){
    int ans=0;
    for(int i=1;i<=99;i+=2) ans+=i*(i+1);
    printf("%d\n",ans);
    return 0;
}

附加题2

#include <stdio.h>
int main(){
    double ans=0,n=1;
    for(double i=1;i<=20;i++){
        n*=i;
        ans+=1/n;
    }
    printf("%lf\n",ans);
    return 0;
}

附加题3

#include <stdio.h>
#include <math.h>
int main(){
    double a,b,c,d;
    scanf("%lf%lf%lf",&a,&b,&c);
    d=b*b-4*a*c;
    if(d<0) printf("无解\n");
    else if(d==0) printf("一个解：%lf",-b/(2*a));
    else printf("两个不同解：%lf %lf",(-b+d)/(2*a),(-b-d)/(2*d));
    return 0;
}