#include  <stdio.h>
#include  <windows.h>
int  main()
{
        int  mdays[12]  =  {31,28,31,30,31,30,31,31,30,31,30,31};
        int  y,m,d,r=0,i,w,n;
        printf("Input year month day:\n");
        scanf("%d %d %d",&y,&m,&d);
        if(y%400==0  ||  (y%4==0  &&  y  %100  !=  0))
                mdays[1]  =  29;
        if(y<0  ||  m<=0  ||  m>12  ||  d<=0  ||  d>mdays[m-1])
        {
                printf("大宝贝儿，你输入年月日不对哦~\n");
                return  -1;
        }
        for(i  =  0;  i  <  m-1;  i  ++)
                r+=mdays[i];
        r+=d;
        w=y-1+(y-1)/4-(y-1)/100+(y-1)/400+r;
        n=w%7;
        {
        if(n=0)  
        printf("%d  SUNDAY\n",r);
        else
        printf("%d   %d\n",r,n);
        }
        return  0;
}

if (n == 0)

谢谢，非常感谢！