#include"stdio.h"

typedefstructdate

{

intyear;

intmonth;

intday;

}date;

char*week[]={"星期日","星期一","星期二","星期三","星期四","星期五","星期六"};

intdays[]={31,28,31,30,31,30,31,31,30,31,30,31};

intisleapyear(intyear);

voidlistdate(intweekday,datenow,intdiff);

/*知道今天星期幾以及年月日，編寫c程式，要求能算出任意天后是星期幾以及年月日*/

voidmain()

{

intweekday;

datenow;

intdiff;

printf("請輸入今天是星期幾以及日期");

printf("星期幾(0..6，星期日..星期六)：");

scanf("%d",&weekday);

printf("日期(yyyy-mm-dd):");

scanf("%d-%d-%d",&now.year,&now.month,&now.day);

printf("相隔天數：");

scanf("%d",&diff);

listdate(weekday,now,diff);

}

/*判斷閏年*/

intisleapyear(intyear)

{

return((year%400==0)||(year%4==0&&year%100!=0))?1:0;

}

/*已知今天是星期幾(weekday，0..6，sunday..saturday)以及日期(now)，輸出diff天后是星期幾以及日期*/

/*diff>0指diff天后，diff

voidlistdate(intweekday,datenow,intdiff)

{

intw1;

dated1;

/*計算diff天后是星期幾*/

w1=weekday+diff;

while(w1

{

w1+=7;

}

w1=w1%7;

printf("%d天后：\n",diff);

printf("%s\n",week[w1]);

/*計算diff天的日期*/

d1.year=now.year;

d1.month=now.month;

d1.day=now.day+diff;

if(d1.day>0)

{

while(d1.day>days[d1.month-1])

{

d1.day-=days[d1.month-1]+(d1.month==2&&isleapyear(d1.year));

d1.month++;

if(d1.month>12)

{

d1.month=1;

d1.year++;

}

}

}

elseif(d1.day

{

while(d1.day

{

d1.month--;

if(d1.month

{

d1.month=12;

d1.year--;

}

d1.day+=days[d1.month-1]+(d1.month==2&&isleapyear(d1.year));

}

}

printf("%d-%d-%d\n",d1.year,d1.month,d1.day);

}