用c语言编写万年历程序

以下是一个简单的用 C 语言编写的万年历程序，可以根据输入的年份和月份输出对应的日历：

#include <stdio.h>

int main() {
    int year, month, day, week;
    int days_in_month[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    char *weekdays[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

    printf("Enter year: ");
    scanf("%d", &year);

    printf("Enter month: ");
    scanf("%d", &month);

    day = 1;
    week = 0;

    // check for leap year
    if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
        days_in_month[2] = 29;
    }

    // calculate weekday of 1st day of month
    for (int i = 1; i < month; i++) {
        day += days_in_month[i];
    }
    week = (year + year / 4 - year / 100 + year / 400 + day) % 7;

    // print calendar
    printf("\n     %d/%d\n", month, year);
    printf("--------------------\n");
    printf("Sun Mon Tue Wed Thu Fri Sat\n");
    printf("--------------------\n");
    for (int i = 0; i < week; i++) {
        printf("    ");
    }
    for (int i = 1; i <= days_in_month[month]; i++) {
        printf("%3d ", i);
        if (++week > 6) {
            week = 0;
            printf("\n");
        }
    }
    printf("\n");

    return 0;
}

其中，我们首先输入年份和月份，然后判断该年是否为闰年，计算出该月的第一天是星期几，最后根据每个月的天数和第一天是星期几，输出对应的日历。