请用c语言编写程序，输入年份和月份，输出该月的月历

以下是一个简单的 C 语言程序，用于输出指定年份和月份的月历：

#include <stdio.h>

int is_leap_year(int year)
{
    return ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);
}

int get_days_in_month(int year, int month)
{
    int days_in_month[] = {31, 28 + is_leap_year(year), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    return days_in_month[month - 1];
}

void print_calendar(int year, int month)
{
    int days_in_month = get_days_in_month(year, month);
    int day_of_week = 1;
    
    // Print the month and year
    printf("%d/%d\n", month, year);
    printf("Su Mo Tu We Th Fr Sa\n");
    
    // Print the days of the month
    for (int day = 1; day <= days_in_month; day++) {
        // Print leading spaces for the first week
        if (day == 1) {
            for (int i = 1; i < day_of_week; i++) {
                printf("   ");
            }
        }
        
        // Print the day
        printf("%2d ", day);
        
        // Print a newline if it's the end of the week
        if (day_of_week == 7 || day == days_in_month) {
            printf("\n");
            day_of_week = 1;
        } else {
            day_of_week++;
        }
    }
}

int main()
{
    int year, month;
    
    // Prompt the user for input
    printf("Enter the year: ");
    scanf("%d", &year);
    printf("Enter the month: ");
    scanf("%d", &month);
    
    // Print the calendar
    print_calendar(year, month);
    
    return 0;
}

该程序使用 `is_leap_year` 函数判断是否为闰年，使用 `get_days_in_month` 函数获取指定月份的天数。接下来，程序使用 `print_calendar` 函数打印月历。在此函数中，程序首先打印月份和年份，然后打印每个日期。该函数使用一个计数器 `day_of_week` 跟踪每周的天数，并在每周的末尾打印一个换行符。