星期几 知道今天(2013年8月9号星期五)

bool runnian(int y){return (y%4==0&&y%100!=0)||y%400==0;}int fm(int y,int m,int d){switch (m){case 1:if(!runnian(y)) return -(9+31+30+31+30+31+28+31-d);else return -(9+31+30+31+30+31+29+31-d);break;case 2:if(!runnian(y)) return -(9+31+30+31+30+31+28-d);else return -(9+31+30+31+30+31+29-d);break;case 3:return -(9+31+30+31+30+31-d);break;case 4:return -(9+31+30+31+30-d);break;case 5:return -(9+31+30+31-d);break;case 6:return -(9+31+30-d);break;case 7:return-(9+31-d);break;case 8:if(d>=9)  return (d-9);else  return -(9-d);break;case 9:return (22+d); break;case 10:return (22+30+d); break;case 11:return (22+30+31+d); break;case 12:return (22+30+31+30+d); break;}}int f(int y,int m,int d){int day=0;if(y==2013)  day=fm(y,m,d);if(y<2013){for (int i=2013;i>y;i--){if(runnian(i)) day+=366;else day+=365;}day-=fm(y,m,d);day=-day;}if(y>2013){for (int i=y;i>2013;i--){if(runnian(i)) day+=366;else day+=365;}day=day+fm(y,m,d);}if(day>=0) return (5+day)%7==0?7:(5+day)%7;else  return 5-(-day)%7>0?5-(-day)%7:5-(-day)%7+7;}void main(){cout<<f(20,8,8);system("pause");}