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为了解决这个问题，我们需要根据给定的天数计算出对应的日期和星期几。从2000年1月1日开始，逐日递减天数，直到找到目标日期。我们将使用C语言来实现这一功能。

方法思路

解决代码

#include 
   
    
char week[7][10] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
int year_type[2] = {365, 366}; // 0:平年, 1:闰年
int month_day[2][12] = {31,28,31,30,31,30,31,31,30,31,30,31,31,29,31,30,31,30,31,31,30,31,30,31};
int type(int m) {
    if (m % 4 != 0 || (m % 100 == 0 && m % 400 != 0)) {
        return 0;
    } else {
        return 1;
    }
}
int main() {
    int days, dayofweek;
    int i = 0, j = 0;
    while (scanf("%d", &days) != -1) {
        if (days == -1) {
            break;
        }
        int current_days = days;
        int year_count = 0;
        int month_count = 0;
        int current_year = 2000;
        int current_month = 0;
        int current_day = 1;
        // 计算年份
        while (current_days > 0) {
            int is_leap = type(current_year);
            int total_days_in_year = is_leap ? 366 : 365;
            if (current_days >= total_days_in_year) {
                year_count++;
                current_days -= total_days_in_year;
            } else {
                break;
            }
            current_year += 1;
        }
        // 计算月份和日期
        if (current_days > 0) {
            current_month = current_year;
            current_year = 2000;
            j = 0;
            while (current_days > 0) {
                int month_days = month_day[is_leap ? 1 : 0][j];
                if (current_days >= month_days) {
                    j++;
                    current_days -= month_days;
                } else {
                    current_day = current_days + 1;
                    break;
                }
            }
        } else {
            current_day = current_days + 1;
        }
        // 计算星期几
        dayofweek = current_day % 7;
        if (dayofweek < 0) {
            dayofweek += 7;
        }
        // 输出结果
        printf("%04d-%02d-%02d%s\n", current_year, current_month, current_day, week[dayofweek]);
    }
}
   

代码解释

通过这种方法，我们能够准确地计算出从2000年1月1日开始的任意天数对应的日期和星期几。