C语言 练习1-计算两个日期的间隔天数

#include <stdio.h>
#include <stdlib.h>

int daynumber(int year,int mon,int day)//返回日期在当年是第几天
{
	int a[]={31,28,31,30,31,30,31,31,30,31,30,31};
	int i,total=0;
	for(i=0; i<mon-1; i++)
	{
		total+=a[i];
	}
	if(mon>2) //算闰年不能放到for里面
	{
		total+=(year%4==0&&year%100!=0 || year%400==0);
	}
	total+=day;
	//printf("%04d-%02d-%02d is %dth days\n",year,mon,day,total);
	return total;
}

int yearnumber(int year1,int year2)
{
	int total=0,year;
	for(year=year1; year<year2; year++)
	{
		total+=365+(year%4==0&&year%100!=0 || year%400==0);
	}
	return total;
}

int main()
{
	int year1,mon1,day1,year2,mon2,day2;
	int dist;
	printf("请输入起始日期 年月日之间用空格隔开\n例如：2019 01 01 2020 12 31\n");
	while(fflush(stdin),//默认year1<year2
		scanf("%d%d%d%d%d%d",&year1,&mon1,&day1,&year2,&mon2,&day2)!=EOF)
	{
		if(year1==year2)
		{
			dist=daynumber(year2,mon2,day2)-daynumber(year1,mon1,day1);
		}else{
			dist=
				 daynumber(year2,mon2,day2)
				+yearnumber(year1,year2)
				-daynumber(year1,mon1,day1);
		}
		printf("%04d-%02d-%02d和%04d-%02d-%02d相差%d天\n",
				year1,mon1,day1,year2,mon2,day2,
				dist);
	}
	
	system("pause");
}