#include<stdio.h>
void main()
{
  int year,leap;
  scanf("%d",&year);
  if(year%4==0)
   {
     if(year%100==0)
      {
        if(year%400==0)
           leap=1;
        else
           leap=0;
      }
    else
      leap=1;
   }
  else
    leap=0;
  if(leap)  
     printf("%d is",year);
  else
     printf("%d is not",year);
  printf("a leap year.\n");
}

while(scanf("%d",year)!=-1)
                 这里应该是scanf("%d",&year）吧

888不是闰年么？   我觉得你写得没有什么问题呀，  加地址符，   while循环还是要留的，   毕竟题目要求了，   逻辑上也没有错误，   要不你换个编译器试试？

/*计算两个日期之间的天数。注：判断年份是否为闰年的方法——为400的倍数为闰年，如2000年；若非100的倍数，而是4的倍数，为闰年
//，如1996年。编程可用素材：printf("from the date (****//**):\n")...、printf("to the date(****//**):\n")、
printf("\nsum=%d\n"...。
*/

#include<stdio.h>

int sb(int yy);

int alldays( int yy, int mm, int dd);

int main(void)
{   
    int yy1, yy2, mm1, mm2, dd1, dd2, sum;

    printf("from the date (****/**/**):\n");
    scanf("%d/%d/%d", &yy1, &mm1, &dd1);

    printf("to the date(****/**/**):\n");
    scanf("%d/%d/%d", &yy2, &mm2, &dd2);

    sum = alldays(yy1, mm1, dd1) - alldays(yy2, mm2, dd2);
    if ( sum < 0)
    {
        sum = -sum;
    }
    printf("\nsum=%d\n", sum);
    return 0;



}

int sb(int yy)

{   
    if ( yy % 4 == 0 && yy % 100 != 0 || yy % 400 == 0)
    {
        return 1;
    }
    return 0;
   
}

int alldays( int yy, int mm, int dd)
{
    int i, sum = dd;
    int data[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    for ( i = 1; i < mm; i++)
    {
        sum = sum + data[i];
    }
    for ( i = 1; i < yy; i++)
    {
        sum = sum + 365 + sb(i);
    }

    return sum;


}

#include<stdio.h>

int main()
{
    int year = 0;
    bool leap;
    while(scanf("%d",&year) != -1)
    {
        if(year % 4 == 0)
        {
            if(year % 100 == 0)
            {
                if(year % 400 == 0)
                    leap = true;
                else
                    leap = false;
            }
            else
                leap = true;
        }
        else
            leap = false;
        if(leap == true)
            printf("%d是闰年\n",year);
        else
            printf("%d不是闰年\n",year);
    }
        return 0;
    }