程序代码：

#include<stdio.h>
int week(int,int);
int main()
    {
    int year;
    scanf("%d",&year);
    for(int i=1; i<13; i++)
        if(week(year,i)==5)
            printf("%d年%d月13日是黑色星期五\n",year,i);//注某月的１３日是星期五称为黑色星期五． 
    return 0;
    }
int week(int year,int month)
    {
    if(month<3)
        {
        month+=12;
        year--;
        }
    return (13+2*month+3*(month+1)/5+year+year/4-year/100+year/400)%7+1;
    }

[此贴子已经被作者于2018-6-6 23:40编辑过]