用c++设计该日在本年中的第几天

#include<iostream.h>
int leapyear(int year);
void main()
{
int year,mon,day;
static int day1[]={31,29,31,30,31,30,31,31,30,31,30,31}; //闰年
static int day2[]={31,28,31,30,31,30,31,31,30,31,30,31}; //非闰年
cout<<"年:";
cin>>year;
cout<<"月:";
cin>>mon;
cout<<"日:";
cin>>day;
int today=day;
for (int m=0;m<mon-1;m++)
{
if (leapyear(year)) today+=day1[m];
else today+=day2[m];
}
cout<<year<<"年"<<mon<<"月"<<day<<"日是该年的第"<<today<<"天"<<endl;
}
int leapyear(int year) //判断year是否为闰年
{
int leap;
if (year%400==0)
leap=1;
else if (year%4==0 && year%100!=0)
leap=1;
else leap=0;
return leap;
}