if判断闰年的程序问题

Question

#include <stdio.h>

int main() 

{ 

    int year,month,day,sum;

char a;    

   loop: do{

  printf("input year,month,day\n");

  scanf("%d.%d.%d",&year,&month,&day);

  if(month>=1&&month<=12&&day>=1&&day<=31) 

  {

    switch(month)

    {

    case 1:sum=day;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 2:sum=day+31;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 3: if(year%400==0||(year%4==0&&year%100!=0))

    {

sum=day+60;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

}

else 

{

sum=day+59;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

}

    case 4:sum=day+90;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 5:sum=day+120;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 6:sum=day+151;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 7:sum=day+181;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 8:sum=day+212;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 9:sum=day+243;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 10:sum=day+273;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 11:sum=day+304;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    case 12:sum=day+334;printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);break;

    default:printf("一年只有12个月哟~\n");break;

     }

    printf("Do you want to continue?y/n\n");

     scanf(" %c",&a);

     }

 else

 {

  printf("Error\n");

  goto loop;

 }

 }while(a=='y'||a=='Y');

return 0;

}

无论闰年非闰年每年的8月8号都显示是220天，其实闰年是221天，也就是判断不了闰年，求解

Answer 1

switch中，你只在三月份的时候判断了一下该年是否为闰年，后面的月份你就不管啦？！