include

void main()
{
int year,month,day;
int yyear,ymonth,yday;
int flag=0;

printf("please input year, month, day:\n");
scanf("%d %d %d",&year,&month,&day);
yyear=year;
ymonth=month;
yday=day;

if(year>9999 || year<1000)
{
    printf("Error，year is between 1000 and 9999!\n");
    flag=1;
}else
{
    if(month>12 || month<1)
    {
        printf("Error,month is between 1 and 12!\n");
        flag=1;
    }else
    {
        if(day>31 || day<1)
        {
            printf("Error,day is between 1 and 31!\n");    
            flag=1;
        }else
        {
            
                if(day<=26 && day >=1)
                {
                    yday=yday+2;                    
                }else if(day==27)
                {
                    if((year%4==0 && year%100!=0)||(year%400==0))
                    {
                        yday=yday+2;
                    }else
                    {    if(month==2)
                        {    
                            yday=1;
                            ymonth=ymonth+1;
                        }else
                        {
                            yday=yday+2;
                        }
                    }
                }else if(day==28)
                {
                    if(month==2)
                    {
                        if((year%4==0 && year%100!=0)||(year%400==0))
                        {
                            yday=1;
                            ymonth=ymonth+1;
                        }else
                        {
                            yday=2;
                            ymonth=ymonth+1;
                        }
                    }else
                    {
                        yday=yday+2;
                    }    
                }else if(day==29)
                {
                    if(month==2)
                    {
                    
                        if((year%4==0 && year%100!=0)||(year%400==0))
                        {
                            yday=2;
                            ymonth=ymonth+1;
                        }else
                        {
                            printf("The day can not be 29 for common year!\n");
                            flag=1;
                        }
                    }else
                    {
                        if(month==4 || month==6|| month==9|| month==11)
                        {
                            yday=1;
                            ymonth=ymonth+1;
                        }else
                        {
                            yday=yday+2;
                        }
                    }
                }else if(day==30)
                {
                    if(month==2)
                    {
                        printf("The day is between 1 and 29!\n");
                        flag=1;
                    }else
                    {
                        if(month==4 || month==6|| month==9|| month==11)
                        {
                            yday=2;
                            ymonth=ymonth+1;
                        }else
                        {
                            yday=1;
                            ymonth=ymonth+1;
                        }
                    }
                }else if(day==31)
                {
                    if(month==12)
                    {
                        yday=2;
                        ymonth=1;
                        yyear=yyear+1;
                    }else
                    {
                        if(month==2 || month==4 || month==6|| month==9|| month==11)
                        {
                            printf("Error!\n");
                            flag=1;
                        }else
                        {
                            yday=2;
                            ymonth=ymonth+1;
                        }
                    }
                }
                
        }    
    }
}
if(flag!=1)
{
    printf("The day after tomorrow is:\n");
    printf("%d,%d,%d\n",yyear,ymonth,yday);
}

}

谁写的垃圾代码，我都不用知道他最终到底要干什么，只看这逻辑反反复复的，一遍又一遍的，就没有任何看懂的价值
你好好把原题目发出来，我给你压缩到这个代码行数的1/3

• 可以看下c语言参考手册中的 c语言-注释

这不就是求年月日的下一天嘛。为啥要写的这么复杂