该日在本年第几天

/*
 *Copyright (c) 2016 烟台大学计算机与控制工程学院
 *All rights reserved.
 *文件名称：test.cpp
 *作    者：史红浩
 *完成日期：2016年 6 月 21 日
 *问题描述：定义一个结构体变量（包括年、月、日）。编写一个函数days，由主函数将年、月、日传递给函数days，计算出该日在本年中是第几天并将结果传回主函数输出。
 *输入描述：年月日
 *输出描述：当年第几天
 *版 本 号：v1.0
*/
#include <iostream> 
using namespace std; 
struct y_m_d
{ 
    int year; 
    int month; 
    int day; 
}; 
 
int days(y_m_d d)
{  
    if(d.year%4==0&&d.year%100!=0||d.year%400==0) 
    { 
        if(d.month==1) 
            return d.day; 
        else if(d.month==2) 
            return d.day+31; 
        else if(d.month==3) 
            return d.day+31+29; 
        else if(d.month==4) 
            return d.day+31+29+31; 
        else if(d.month==5) 
            return d.day+31+31+29+30;       
        else if(d.month==6) 
            return d.day+31+31+31+29+30;    
        else if(d.month==7) 
            return d.day+30+31+31+30+29+30; 
        else if(d.month==8) 
            return d.day+31+31+31+30+29+30+31; 
        else if(d.month==9) 
            return d.day+31+31+31+30+29+30+31+31; 
        else if(d.month==10) 
            return d.day+31+31+31+30+29+30+30+31+31; 
        else if(d.month==11) 
            return d.day+31+31+31+30+29+30+31+31+31+30; 
        else if(d.month==12) 
            return d.day+31+31+31+30+29+30+31+31+31+30+30; 
    } 
    else
    { 
        if(d.month==1) 
            return d.day; 
        else if(d.month==2) 
            return d.day+31; 
        else if(d.month==3) 
            return d.day+31+28; 
        else if(d.month==4) 
            return d.day+31+28+31; 
        else if(d.month==5) 
            return d.day+31+31+28+30;       
        else if(d.month==6) 
            return d.day+31+31+31+28+30;    
        else if(d.month==7) 
            return d.day+30+31+31+30+28+30; 
        else if(d.month==8) 
            return d.day+31+31+31+30+28+30+31; 
        else if(d.month==9) 
            return d.day+31+31+31+30+28+30+31+31; 
        else if(d.month==10) 
            return d.day+31+31+31+30+28+30+30+31+31; 
        else if(d.month==11) 
            return d.day+31+31+31+30+28+30+31+31+31+30; 
        else if(d.month==12) 
            return d.day+31+31+31+30+28+30+31+31+31+30+30; 
    } 
   
}
int main()
{
    y_m_d 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;
}

运行结果：