程序代码：

#include<stdio.h>
int week(int x,int y ,int z)
{
    int i,g,k;
    if(x%400==0)
    {
        i=2;
        switch(y)
        {
          case 1:g=0;break;
            case 2:g=3;break;
          case 3:g=4;break;
          case 4:g=0;break;
          case 5:g=2;break;
          case 6:g=5;break;
          case 7:g=0;break;
          case 8:g=3;break;
          case 9:g=6;break;
          case 10:g=1;break;
          case 11:g=4;break;
          case 12:g=6;break;
        }
    }
    else
    {
        i=1;
        switch(y)
        {
         case 1:g=0;break;
         case 2:g=3;break;
         case 3:g=3;break;
         case 4:g=6;break;
         case 5:g=1;break;
         case 6:g=4;break;
         case 7:g=0;break;
         case 8:g=3;break;
         case 9:g=5;break;
         case 10:g=0;break;
         case 11:g=3;break;
         case 12:g=5;break;
        }
    }
    k=(x+x/4+x/400-x/100-i+g+z)%7;   

    return(k);
}

main()
{
    int y,m,d;
    printf("请输入年月日：");
    scanf("%d%d%d",&y,&m,&d);
    getchar();
    printf("对应的星期数：%d",week(y,m,d));
}