偶然的机会看到了一个计算星期几的算法，感觉很怪异并且很有意思就记录一下，也与大家共勉。自己写的代码有些瑕疵，但重点是计算星期的算法值得思索。

问题：输入年月日计算是星期几？

代码如下：

#include <stdio.h>

int getWeek(int year, int month, int day)

{

int aWeek[12] = {0,3,2,5,0,3,5,1,4,6,2,4};

int week = 0;

int temp = 0;

if(year < 1 || month < 1 || month > 12 || day < 1 || day > 31)

{

return 0;

}

year -= month < 3;

temp = (year + year/4 - year/100 + year/400 + aWeek[month-1] + day) % 7;

switch(temp)

{

case 0: week = 7;break;

case 1: week = 1;break;

case 2: week = 2;break;

case 3: week = 3;break;

case 4: week = 4;break;

case 5: week = 5;break;

case 6: week = 6;break;

default: week = 0;break;

}

return week;

}

int main()

{

int year = 0;

int month = 0;

int day = 0;

int week = 0;

while(1)

{

printf("Please input date:(year month day)\n");

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

week = getWeek(year, month, day);

if(week < 1 || week > 7)

return 0;

printf("date:%d-%d-%d is %d of week\n", year, month, day, week);

}

return 0;

}