Created
December 24, 2015 08:06
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萬年曆。從2000年起算，0代表星期一，6代表星期日。
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| #include<stdio.h> | |
| #include<stdlib.h> | |
| int is_leap_year(int year){ | |
| if((year - 2000)%400==0) | |
| return 1; | |
| else if((year - 2000)%100 == 0) | |
| return 0; | |
| else if((year - 2000)%4 == 0) | |
| return 1; | |
| else | |
| return 0; | |
| } | |
| int cal_week_day(int year, int month, int day){ | |
| const int year2000_start_week_day = 5;//0-base, 2000/1/1 is Saturday | |
| int year_start_week_day = 0;//week day of JAN 1st | |
| int week_day = 0; | |
| int common_year_week_day_offset[12] = {0,3,3,6,1,4,6,2,5,0,3,5}; | |
| int leap_year_week_day_offset[12] = {0,3,4,0,2,5,0,3,6,1,4,6}; | |
| //find the start week day of the year | |
| year_start_week_day = year2000_start_week_day; | |
| if(year > 2000){ | |
| year_start_week_day += (year - 2000)*365; | |
| year_start_week_day += 1;//because 1/1-12/31 is 365 days, the 1/1 of next year is the 366th day. | |
| } | |
| if(year - 2000 >= 4){ | |
| year_start_week_day += (year - 2000) / 4; | |
| } | |
| if(year - 2000 >= 100){ | |
| year_start_week_day -= (year - 2000) / 100; | |
| } | |
| if(year - 2000 >= 400){ | |
| year_start_week_day += (year - 2000) / 400; | |
| } | |
| year_start_week_day %= 7; | |
| //find week day | |
| if(is_leap_year(year)){ | |
| week_day = (year_start_week_day + leap_year_week_day_offset[month-1] + (day-1))%7; | |
| }else{ | |
| week_day = (year_start_week_day + common_year_week_day_offset[month-1] + (day-1))%7; | |
| } | |
| return week_day; | |
| } | |
| int main(int argc, char* argv[]){ | |
| int year = atoi(argv[1]); | |
| int month = atoi(argv[2]); | |
| int day = atoi(argv[3]); | |
| //printf("%d/%d/%d week day(1-7):%d\n",year,month,day,cal_week_day(year,month,day)+1); | |
| printf("%d/%d/%d week day(0-6):%d\n",year,month,day,cal_week_day(year,month,day)); | |
| } |
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