2020 优必选笔试题——计算某一天是周几

蔡勒（Zeller）公式
W=Y+[Y/4]+[C/4]-2C+[26(M+1)/10]+d-1
公式中的符号含义如下：
W为星期数；C为世纪；Y为年（两位数）； M为月数（M=m（当m>2）；M=m+12（m<3））；d为日。

#include

using namespace std;

int getResult(int year, int month, int day) {
   int week = 0;
   int y = 0, m = 0, d = 0, r = 0;
   if (month == 1 || month == 2) {
      r = (year - 1) / 100;
      y = (year - 1) % 100;
      m = month + 12;
      d = day;
   }
   else {
      r = year / 100;
      y = year % 100;
      m = month;
      d = day;
   }
   week = y + y / 4 + r / 4 - 2 * r + 26 * (m + 1) / 10 + d - 1;
   week = week >= 0 ? (week % 7) : (week % 7 + 7);
   if (week == 0) {
      week = 7;
   }
   return week;
}

int main()
{
   int year, month, day;
   cin >> year >> month >> day;
   switch (getResult(year, month, day)) {
   case 1:
      cout << "Monday" << endl;
      break;
   case 2:
      cout << "Tuseday" << endl;
      break;
   case 3:
      cout << "Wednesday" << endl;
      break;
   case 4:
      cout << "Thursday" << endl;
      break;
   case 5:
      cout << "Friday" << endl;
      break;
   case 6:
      cout << "Saturday" << endl;
      break;
   case 7:
      cout << "Sunday" << endl;
      break;
   }
   return 0;
}