Day of the Week LeetCode solution in C++

1
class Solution {
2
 public:
3
  int daysOfMonth[2][12] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
4
                            31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
5
  string weekName[7] = {"Sunday",   "Monday", "Tuesday", "Wednesday",
6
                        "Thursday", "Friday", "Saturday"};
7
  bool isleapyear(int year) {
8
    return ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));
9
  }
10
  int daystill1971(int year, int month, int day) {
11
    int count = 0;
12
    int year1 = 1970, month1 = 1, day1 = 1;
13
    while (year1 != year) {
14
      bool b = isleapyear(year1);
15
      if (b)
16
        count += 366;
17
      else
18
        count += 365;
19
      year1++;
20
    }
21
    int b = isleapyear(year1) ? 0 : 1;
22
    for (int i = 0; i < month - 1; i++) count += daysOfMonth[b][i];
23
    count += day - 1;
24
    return count;
25
  }
26
  string dayOfTheWeek(int day, int month, int year) {
27
    int days1 = daystill1971(2019, 9, 8); // today(2019,9,8) is Sunday
28
    int days2 = daystill1971(year, month, day);
29
    int days = (((days2 - days1) % 7) + 7) % 7; // Number of days off
30
    return weekName[days];
31
  }
32
};