用C++写一个程序,判断某年某月某日是星期几

在C++中，我们可以使用Zeller's congruence算法或者直接依赖于C库（如`<ctime>`）来计算某年某月某日是星期几。这里是一个简单的Zeller's congruence的例子，它不需要依赖外部库：

#include <iostream>

// Zeller's Congruence function to calculate day of the week
int getDayOfWeek(int year, int month, int day) {
    if (month < 3) {
        month += 12;
        year--;
    }

    int century = year / 100;
    int year_of_century = year % 100;

    int day_of_week = (day + 13 * (month + 1) / 5 + year_of_century + year_of_century / 4 + century / 4 + 5 * century) % 7;

    // Convert numbers from 0-6 to corresponding weekday names (0 is Sunday)
    switch (day_of_week) {
        case 0:
            return "Sunday";
        case 1:
            return "Monday";
        case 2:
            return "Tuesday";
        case 3:
            return "Wednesday";
        case 4:
            return "Thursday";
        case 5:
            return "Friday";
        case 6:
            return "Saturday";
    }
}

int main() {
    int year, month, day;
    std::cout << "Enter a date in format (YYYY MM DD): ";
    std::cin >> year >> month >> day;

    std::string dayOfWeek = getDayOfWeek(year, month, day);
    std::cout << "The date " << year << "-" << month << "-" << day << " is " << dayOfWeek << "." << std::endl;

    return 0;
}

当你运行这个程序并输入特定日期，它会告诉你那天是星期几。记得Zeller's congruence只适用于公元后的日期。