用C++中switch语句编写程序，键盘输入任意年和月号，输出该年该月有几天?

#include <stdio.h>

int main() {
    int year, month, days;

    printf("请输入年份和月份，格式为yyyy mm：");
    scanf("%d %d", &year, &month);

    switch (month) {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            days = 31;
            break;
        case 4:
        case 6:
        case 9:
        case 11:
            days = 30;
            break;
        case 2:
            if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
                days = 29;
            } else {
                days = 28;
            }
            break;
        default:
            printf("输入的月份不合法。\n");
            return 0;
    }

    printf("%d年%d月有%d天。\n", year, month, days);

    return 0;
}

注意：闰年判断的算法为：四年一润，百年不润，四百年再润。因此，能被4整除而不能被100整除的年份是闰年，能被400整除的年份也是闰年。