利用switch语句解决问题：年月日

#include 
int main ( )
{
    int  year, month, days;
    printf("请输入年、月: ");
    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;
    }
    printf("%d 年 %d 月共有 %d 天。\n", year, month, days);
    return 0;
}