2000年一月一日是星期二，输入2000年的某月某日，输出是星期几？ 这个程序用c语言怎么写？？？？

#include

void main()
{
int i,n=0,month,day;
int month_day[]={31,29,31,30,31,30,31,31,30,31,30,31};
char str[7][10]={"星期天","星期一","星期二","星期三","星期四","星期五","星期六"};
printf("请输入月、日：");
scanf("%d%d",&month,&day);
for(i=1;i n=n+month_day[i-1];
n=n+day;
n=(n+1)%7;
printf("2000年%d月%d日是%s\n",month,day,str[n]);
}

#include
void main ()
{
int y,m,d,c,s,w;
printf("请输入8位年月日,以空格隔开：");
scanf("%d%d%d",&y,&m,&d);
if (m==1) c=d;
else if (m==2) c=31+d;
else if (m==3) c=31+28+d;
else if (m==4) c=31+28+31+d;
else if (m==5) c=31+28+31+30+d;
else if (m==6) c=31+28+31+30+31+d;
else if (m==7) c=31+28+31+30+31+30+d;
else if (m==8) c=31+28+31+30+31+30+31+d;
else if (m==9) c=31+28+31+30+31+30+31+31+d;
else if (m==10) c=31+28+31+30+31+30+31+31+30+d;
else if (m==11) c=31+28+31+30+31+30+31+31+30+31+d;
else if (m==12) c=31+28+31+30+31+30+31+31+30+31+30+d;
if (m>2)
{if (y%100==0) {if (y%400==0) c=c+1;}
else if (y%4==0) c=c+1;}
s=(y-1)*365+(y-1)/4-(y-1)/100+(y-1)/400+c;
w=s%7;
switch (w)
{
case 0: printf("星期日");break;
case 1: printf("星期一");break;
case 2: printf("星期二");break;
case 3: printf("星期三");break;
case 4: printf("星期四");break;
case 5: printf("星期五");break;
case 6: printf("星期六");break;
printf("\n");
}
}