给你一个日期，请你设计一个算法来判断它是对应一周中的哪一天。

输入为三个整数：day、month 和 year，分别表示日、月、年。

您返回的结果必须是这几个值中的一个 {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}。

示例 1：

输入：day = 31, month = 8, year = 2019
输出："Saturday"
示例 2：

输入：day = 18, month = 7, year = 1999
输出："Sunday"
示例 3：

输入：day = 15, month = 8, year = 1993
输出："Sunday"
 

提示：

给出的日期一定是在 1971 到 2100 年之间的有效日期。

class Solution {
public:
    string dayOfTheWeek(int day, int month, int year) {
        vector<string> week = {"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
        vector<int> Monthdays = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30};
        int days = 365*(year - 1971) + (year - 1969) / 4;
        for(int i = 0; i < month - 1; i++) {
            days += Monthdays[i];
        }
        if(((year % 400 == 0) || (year % 4 == 0 &&  year % 100 != 0)) && month > 3) {
            days += 1;
        }
        days += day;
        return week[(days + 3) % 7];
    }
};