#include<stdio.h>
#include<windows.h>
int main()
{
      int i,j=0,k=0;
      printf("enter a number:");
      scanf("%d",&i);
      
      while(i!=-1)
      {if(i>=j)
       {j=i;
       printf("enter a number:");
       scanf("%d",&i);}
          else if(i>=k)
         { k=i;
           printf("enter a number:");
           scanf("%d",&i);}
           else
           {printf("enter a number:");
            scanf("%d",&i);}}
       printf("the biggest is:%d\n",j);
       printf("the bigger is:%d\n",k);
       system("pause");
       return 0;}
这里第二大的值为什么算不出来呢

你算法本身就有问题吧
比如
i = 5时，J = 5，K=0；
I = 8时，J = 8，K=0；
I = 4时，J = 8，K =4 ；
I=-1；
输出 8，4  
所以你算法本身就是错了.........


还有程序要排好版，方便自己也方便别人看...

#include<stdio.h>
#include<windows.h>

int main()
{
      int i, j = 0, k = 0;
      printf("enter a number:");
      scanf("%d",&i);

      while(i!=-1)
      {
          if(i >= j)
          {
              /* 加上这句 */
              k = j;
              j = i;
              printf("enter a number:");
              scanf("%d", &i);
          }
          else if(i >= k)
          {
              k = i;
              printf("enter a number:");
              scanf("%d", &i);
          }
          else
          {
              printf("enter a number:");
              scanf("%d", &i);
          }
       }

       printf("the biggest is:%d\n", j);
       printf("the bigger is:%d\n", k);
       system("pause");

       return 0;
}

xiexie