题解 | #Day of Week#

#include <stdio.h>
#include <string.h>

//闰年返回1
int IsLeapYear(int year){
    return (year%400 == 0 || (year%100 != 0 && year%4 == 0));
}

int main() {
    int day, year;
    char mon[14];
    char month[13][14] = {"","January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
    char week[7][14]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
    int mon_day[2][13] = {{0,31,28,31,30,31,30,31,31,30,31,30,31},
    {0,31,29,31,30,31,30,31,31,30,31,30,31}};
  
    while (scanf("%d %s %d", &day, mon, &year) != EOF) {
        int _day = 0;
        //获取给定年份日期相对于1年1月1日过去了天
        for (int i = 1; i < year; ++i) {
            _day += 365 + IsLeapYear(i);
        }
        int j = 0;
        //再加上 给定年份的月所对应前面的天数
        while (strcmp(mon, month[j]) != 0) {
            _day += mon_day[IsLeapYear(year)][j++];
        }
	  	//最后再加上天数
        _day += day;
        int w = _day%7;
        printf("%s\n",week[w]);
    }
    return 0;
}