codeup之Day of Week（给定日期判断周几

题目描述

We now use the Gregorian style of dating in Russia. The leap years are years with number divisible by 4 but not divisible by 100, or divisible by 400.
For example, years 2004, 2180 and 2400 are leap. Years 2004, 2181 and 2300 are not leap.
Your task is to write a program which will compute the day of week corresponding to a given date in the nearest past or in the future using today’s agreement about dating.

输入

There is one single line contains the day number d, month name M and year number y(1000≤y≤3000). The month name is the corresponding English name starting from the capital letter.

输出

Output a single line with the English name of the day of week corresponding to the date, starting from the capital letter. All other letters must be in lower case.

样例输入

21 December 2012
5 January 2013

样例输出

Friday
Saturday

idea

• 利用基姆拉尔森计算公式
  W= (d+2m+3(m+1)/5+y+y/4-y/100+y/400+1)%7
  其中，w为周几，0~6对应周日，周一，周二……周六
  年y，月m， 日d
  1月换为13月，2月换为14月

solution

#include <stdio.h>
#include <string.h>
int main(){
	char month[12][20] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
	char week[7][20] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
	int d, m, y, w;
	char mm[20];
	while(scanf("%d %s %d", &d, mm, &y) != EOF){
		for(int i = 0; i < 12; i++){
			if(strcmp(mm, month[i]) == 0){
				m = i + 1;
				break;
			}
		}
		if(m == 1 || m == 2){
			m = ((m == 1) ? 13 : 14);
			y--;
		}
		w = (d + 2*m + 3*(m+1)/5+y+y/4-y/100+y/400+1)%7;
		printf("%s\n", week[w]);
		memset(mm, '\0', sizeof(mm));
	}
	return 0;
}