# include <stdio.h>
int main (void)
{
    int a;
    int c;
    int b;
    int i;
    scanf("%d\n", &a);
   
    for(i=0; i<++i+1; ++i)
        
    {  char ch;
      
      
       ch = getchar();
      
       switch(ch)
       {
       case'+':
           scanf("%d", &b);
           c=a + b;
           break;
       case'-':
           scanf("%d", &b);
           c=a - b;
           break;
       case'*':
           scanf("%d", &b);
           c=a * b;
           break;
       case'/':
           scanf("%d", &b);
           c=a / b;
           
           break;  
       }
      
       a = c;
      
    }
        printf("%d\n", c);
    return 0;
   
}

经过自己研究，发现这样可以解决问题，希望可以对出学者一点帮助，大神勿喷
# include <stdio.h>
int main (void)
{
    int a;
    int c;
    int b;
    //int i;
    char ch;
    scanf("%d\n", &a);
   
    while((ch = getchar())!='=')
    {
        
        switch(ch)
        {
        case'+':
            scanf("%d", &b);
            c=a + b;
            break;
        case'-':
            scanf("%d", &b);
            c=a - b;
            //printf("%d", c);
            break;
        case'*':
            scanf("%d", &b);
            c=a * b;
            break;
        case'/':
            scanf("%d", &b);
            c=a / b;
            
            break;  
        }
        
        a = c;
        
    }
    printf("%d\n", c);
    return 0;
   
}