#include<stdio.h>
#define MONTHS 12

int main()
{
    int days[2] [MONTHS] = {{31,28,31,30,31,30,31,31,30,31,30,31},
                            {31,29,31,30,31,30,31,31,30,31,30,31}};
   
    int year, month;
   
    do{
        printf("Input year, month:");
        
        scanf("%d, %d",  &year, &month);

      } while(month < 1 || month > 12);
      
      if ( ( (year%4 == 0)  && (year%100 != 0) )  || (year%400 == 0) )
      
         printf("The number of days is %d\n", days [1] [month-1]);
         
      else
         
         printf("The number of days is %d\n", days [0] [month-1]);
   
    return 0;
}

scanf("%d, %d"  把这里的空格去掉

谢谢！

程序还是不对，它一直让你不停的输入 ：

修改后，这样就可以了。你试试：
#include<stdio.h>
#define MONTHS 12

int main()
{
    int days[2] [MONTHS] = {{31,28,31,30,31,30,31,31,30,31,30,31},
                            {31,29,31,30,31,30,31,31,30,31,30,31}};
   
    int year, month;
   
   
        printf("Input year, month:");
        
        scanf("%d%d",&year, &month);

      
       while(month < 1 || month > 12);
      
      if ( ( (year%4 == 0)  && (year%100 != 0) )  || (year%400 == 0) )
      
         printf("The number of days is %d\n", days [1] [month-1]);
         
      else
         
         printf("The number of days is %d\n", days [0] [month-1]);
   
    return 0;
}

是二月才需要判断吧~其余的是一样的~