编辑代码

#include<stdio.h>
struct  date 
{
     int  year; 
     int  month; 
     int  day; 
}; 

int  leap_year( int  a);
int  cal_day( struct  date a);

/* 判断闰年 */  
int  leap_year( int  a)
{
     if (a % 400 == 0 || (a % 4 == 0 && a % 100 != 0 )) 
         return   1 ;
     else  
         return   0 ;
}

/* 计算一年中的第几天 */  
int  cal_day( struct  date a) 
{
     int  sum = 0 ,b[] = { 31 , 28 , 31 , 30 , 31 , 30 , 31 , 31 , 30 , 31 , 30 , 31 } ;
     for ( int  i = 0 ;i < a.month - 1 ;i ++ ) 
        sum += b[i]; 
     if (a.month > 2 )
        sum = sum + a.day + leap_year(a.year); 
     else
        sum = sum + a.day;
     return  sum; 
} 

void  main()
{
     struct  date a;
     int  n;
    printf( " \n请输入日期（年 月 日）\n " ); 
    scanf( " %d%d%d " , & a.year, & a.month, & a.day); 
    n = cal_day(a);
    printf( " 该日在本年中是第%d天\n " ,n);
}