C++Switch语句实现输入日期计算为改年的第几天

#include<iostream>
using namespace std;
int main()
{
 long year,location;
 int month,day;
 cout<<"请输入年月日："<<endl;
 cin>>year>>month>>day;
 
 if ((year%4==0&&year&100!=0)||(year%400==0))
 {
   switch(month)
   {
   case 1:{location=day;break;}
   case 2:{location=31+day;break;}
   case 3:{location=31+29+day;break;}
   case 4:{location=31+29+31+day;break;}
   case 5:{location=31+29+31+30+day;break;}
   case 6:{location=31+29+31+30+31+day;break;}
   case 7:{location=31+29+31+30+31+30+day;break;}
   case 8:{location=31+29+31+30+31+30+31+day;break;}
   case 9:{location=31+29+31+30+31+30+31+31+day;break;}
   case 10:{location=31+29+31+30+31+30+31+31+30+day;break;}
   case 11:{location=31+29+31+30+31+30+31+31+30+31+day;break;}
   case 12:{location=31+29+31+30+31+30+31+31+30+31+30+day;break;}
   }
 }
 else
 {
   switch(month)
   {
   case 1:{location=day;break;}
   case 2:{location=31+day;break;}
   case 3:{location=31+28+day;break;}
   case 4:{location=31+28+31+day;break;}
   case 5:{location=31+28+31+30+day;break;}
   case 6:{location=31+28+31+30+31+day;break;}
   case 7:{location=31+28+31+30+31+30+day;break;}
   case 8:{location=31+28+31+30+31+30+31+day;break;}
   case 9:{location=31+28+31+30+31+30+31+31+day;break;}
   case 10:{location=31+28+31+30+31+30+31+31+30+day;break;}
   case 11:{location=31+28+31+30+31+30+31+31+30+31+day;break;}
   case 12:{location=31+28+31+30+31+30+31+31+30+31+30+day;break;}
   }
 }
 cout<<year<<"年"<<month<<"月"<<day<<"日"<<"是"<<year<<"年的第"<<location<<"天。"<<endl;
 return 0;
}