C语言实战3：要求输入年月日，输出这是这一年的第几天以及菱形空心输出，还有用 go to 写求质数

一、要求输入年月日，输出这是这一年的第几天

int main ()
{
    int year , mounth , day ;
    printf("请输入今天的年月日，中间用空格隔开\n");
    scanf("%d%d%d",&year,&mounth,&day);
    int dath0 = 31 ;
    int dath1 = 30 ;
    int dath = 0 ;
    int dath2 ;
    if(year / 4 == 0 && year / 100 != 0 || year / 400 == 0 )
        dath2 = 29 ;
    else
        dath2 = 28 ;

    if ( mounth > 1 )
        dath = dath + dath0 ;
    if ( mounth > 2 )
        dath = dath + dath2 ;
    if  ( mounth > 3 )
        dath = dath + dath0 ;
    if  ( mounth > 4 )
        dath = dath + dath1 ;
    if ( mounth > 5 )
        dath = dath + dath0 ;
    if ( mounth > 6 )
        dath = dath + dath1 ;
    if ( mounth > 7 )
        dath = dath + dath0 ;
    if ( mounth > 8 )
        dath = dath + dath1 ;
    if ( mounth > 9 )
        dath = dath + dath1 ;
    if ( mounth > 10 )
        dath = dath + dath0 ;
    if ( mounth > 11 )
        dath = dath + dath1 ;
    if ( mounth > 12 )
        dath = dath + dath0 ;
    dath = dath + day ;
    printf("今天是这一年的第%d天\n",dath);
    return 0 ;
}

二、菱形空心输出

int main()
{
    int a,b,n;
    a = 1 ;
    b = 1 ;
    printf("请输入菱形的棱长\n");
    scanf("%d",&n);
    for(int i = 0 ; i <= n ; i++ )
    {
        for (int m = 0 ; m <= 2*n ; m ++)
        {
            if(m == n-i || m==n+i  )
                printf("*");
            else
                printf(" ");
        }
        printf("\n");
    }
    for(int i = 1 ; i <= n ; i++ )
    {
        for (int m = 0 ; m <= 2*n ; m ++)
        {
            if(m == i || m == 2*n-i  )
                printf("*");
            else
                printf(" ");
        }
        printf("\n");
    }
    return 0 ;
}

三、用 go to 写求质数

int main()
{
    int num1 , num2 ;
    printf("请输入您想找出从几到几的质数\n");
    scanf("%d%d",&num1,&num2);
    //for( int i = num1 ; i < num2 ; i++)
    int i = num1 ;
    start_1_1:
   // {   
        if ( i > num2)
        {
            goto end_1_1 ;
        }
        int a = 2 ;
        //for( int a = 2 ; a <= i ; a++ )
        //{
        start_2_1 :
            if(a > i)
                goto end_2_1 ;
            if(i == a)
            printf("%d  ", i );
            if( i%a == 0 )
            {
                //break ;
                goto end_2_1;
            }
            a++;
            goto start_2_1 ;
        //}
        end_2_1 :
        i++;
        goto start_1_1;
   // }
    end_1_1 :
    return 0 ;
}