用C++编写一个函数求某月有多少天。要求该函数以年份和月份作为函数输入参数，以天数作为返回值。并在主函数中调用该函数输出天数结果。谢谢

#include <stdio.h>

int daysInMonth(int year, int month);

int main() {
    int year, month, days;
    printf("请输入年份和月份(用空格隔开): ");
    scanf("%d %d", &year, &month);
    days = daysInMonth(year, month);
    printf("%d年%d月有%d天\n", year, month, days);
    return 0;
}

int daysInMonth(int year, int month) {
    int days;
    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("输入有误，请输入1-12之间的月份\n");
            days = -1;
    }
    return days;
}