【Ｃ＋＋】判断是否为闰年，是该年的哪一天

//判断是否为闰年，是该年的哪一天
#include <iostream>
using namespace std;
int sum(int month,int day);
int leap(int year);
int main()
{
int year,month,day;
cout<<"请输入一个日期: ";
   cin>>year>>month>>day;
int days=sum(month,day);
if(leap(year)&&month>2)
days++;
cout<<year<<"年"<<month<<"月"<<day<<"日是这一年的第"<<days<<"天。\n";
if(year%4==0&&year%100!=0||year%400==0)
cout<<"该年是闰年";
else cout<<"该年不是闰年";
}
int sum(int month,int day)
{
int day_month[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
for(int i=1;i<month;i++)
day+=day_month[i];
return day;
}
int leap(int year)
{
int leap=year%4==0&&year%100!=0||year%400==0;
return leap;
}