编程实现统计某年某月份的天数。 例如：输入：2017.7 输出：31天

//输入一个月份，计算这个月份的天数
#include<stdio.h>

int main()
{
    int year,mon;
    int leap;
    int days;



    printf("输入年份、月份：\n");
    scanf("%d %d",&year,&mon);

    fun(year);

    switch(mon)
    {
        case 1:
    days = 31;
    break;

    case 2:
    if(leap == 1)
    days = 28;
    else
    days = 29;
    break;

    case 3:
    days = 31;
    break;

    case 4:
    days = 30;
    break;

    case 5:
    days = 31;
    break;

    case 6:
    days = 30;
    break;

    case 7:
    days = 31;
    break;

    case 8:
    days = 31;
    break;

    case 9:
    days = 30;
    break;

    case 10:
    days = 31;
    break;

    case 11:
    days =30;
    break;

    case 12:
    days = 31;
    break;
        
    default:
    printf("你来自火星！\n");
    break;
    }

    printf("%d\n",days);

    return 0;
}

fun (int year)     //用来判断输入的年份是闰年还是非闰年；
{
    int flag = 0; //不是闰年；
    int leap;

    if(year % 4 == 0)
    {
        if(year % 100)
    {
        if(year % 400 == 0)
        {
            flag =1;
        }
    }
    else
    {
        flag = 1;       
    }
    }
    else
    {
        flag = 0;
    }

    if(flag == 1)
    {
        leap = 1;
    }
    else
    {
        leap = 0;
    }

}