课后作业  谢谢啦！！！

用Java改的
#include <stdio.h>
#include <stdlib.h>
int year1,year2,month1,month2,day1,day2;
//判断是否是闰年
bool isLeapYear(int year){
     return ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0));
}

//确保两个日期的先后顺序，日期一在日期二前
void check(){
        if(year1 > year2 || (year1 == year2 && month1 > month2)
                 || ( year1 == year2 && month1 == month2 && day1 > day2 ))
        {
            int tempYear = year1;
            int tempMonth = month1;
            int tempDay = day1;
            year1 =year2;
            month1 = month2;
            day1 = day2;
            year2 = tempYear;
            month2 = tempMonth;
            day2 = tempDay;
        }
    }

    //返回某年某月的天数
int dayOfMonth(int year, int month){
        if (month == 1 || month == 3 || month == 5 || month == 7
                     || month == 8 || month == 10 || month == 12)
                return 31;
        else if(month == 4 || month == 6 || month == 9 || month == 11)
                return 30;
        else if(month == 2){
            if (isLeapYear(year))
                return 29;
            else
                return 28;
        }
        return 0;
    }
        
//该日期与本年第一天的差   
int days(int year, int month, int day){
        int count = 0;
        count += day;
        month--;
        while(month > 0){
            count += dayOfMonth(year,month);
            month--;
        }
        return count;
    }

   
int main(void) {
        int n = 0;
        printf("请输入第一个日期：");
        scanf("%d %d %d",&year1,&month1,&day1);
        printf("请输入第二个日期：");
        scanf("%d %d %d",&year2,&month2,&day2);
        check();//确保两个日期的先后顺序，日期一在日期二前
        
        n = 0;
        n -= days(year1,month1,day1);
        n += days(year2,month2,day2);
        
        while(year1 < year2){
            n += (isLeapYear(year1)?366:365);
            year1++;
            
        }
        printf("日期之差为%d天",n);
        system("pause");
}

谢谢！！