计算该日在本年中是第几天

#include <iostream> 
using namespace std; 
struct y_m_d  //声明结构体类型y_m_d
{ 
    int year; 
    int month; 
    int day; 
}; 
  
  
int days(y_m_d date) 
{ 
    int sum=0; 
    int a[13]={0,31,28,31,30,31,30,31,31,30,31,30,31}; 
    for(int i=0;i<date.month;i++) 
    { 
        sum=sum+a[i]; 
    } 
    sum=sum+date.day; 
    if((date.year%4==0&&date.year%100!=0)||(date.year%400==0)) 
        sum++; //判断是否是闰年
    return sum; 
} 
  
/*int main()


{


    y_m_d date;//定义一个y_m_d的变量date


    int days(y_m_d);  


    int day_sum;


    cin>>date.year>>date.month>>date.day;


    day_sum=days(date);


    cout<<day_sum<<endl;


    return 0;


}
*/