编写—个程序。请求用户键入日、月和年。月份可以是月份号、月份

#include<stdio.h>
int days(int day,int month,int year);
int leapyear(int year);
struct month{
 char name[10];
 char abbrev[4];
 int days;
 int monumb;
};
struct month months[12]={
 {"january",  "jan",31,1},
 {"february", "feb",28,2},
 {"march",  "mar",31,3},
 {"april",  "apr",30,4},
 {"may",   "may",31,5},
 {"june",  "jun",30,6},
 {"july",  "jul",31,7},
 {"august",  "aug",31,8},
 {"september", "sep",30,9},
 {"october",  "oct",31,10},
 {"november", "nov",30,11},
 {"december", "dec",31,12}
};
int main(void)
{
 int day=1,mon=12,year=1,daytotal;
 printf("Enter the number of day,month,year: ");
 while(scanf("%d%d%d", &day, &mon, &year) == 3)
 {
 daytotal = days(day,mon,year);
 if (daytotal > 0)
 printf("There are %d days through day %d, month %d, year %d.\n", daytotal, day, mon, year);
 else
 printf("day %d, month %d, year %d is not valid input.\n", day,mon,year);
 printf("Next month (input q to quit): ");
 }
 puts("bye");
 return 0;
}
int days(int day,int mon,int year)
{
 int i, total;
 if( leapyear(year) ) months[1].days = 29 ;
 else months[1].days = 28 ;
 if (mon < 1 || mon > 12 || day < 1 || day > months[mon-1].days )
 return(-1);  /* error signal */
 else
 {
 for (i = 0, total = 0; i < mon-1; i ++)
 total += months[i].days;
 return( total+day );
 }
}
int leapyear(int year)
{
 if(year%400 ==0 )
 return 1;
 else if(year%100 != 0 && year%4 == 0)
 return 1;
 else return 0;
}