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

prog.c: In function 'main':
prog.c:13:9: error: stray '\357' in program
         case '+'：{c=a+b;printf("%d\n",c);break;}
         ^
prog.c:13:9: error: stray '\274' in program
prog.c:13:9: error: stray '\232' in program
prog.c:13:20: error: expected ':' or '...' before '{' token
         case '+'：{c=a+b;printf("%d\n",c);break;}
                    ^
prog.c:15:10: error: stray '\357' in program
          case '-'：{c=a-b;printf("%d\n",c);break;}
          ^
prog.c:15:10: error: stray '\274' in program
prog.c:15:10: error: stray '\232' in program
prog.c:15:21: error: expected ':' or '...' before '{' token
          case '-'：{c=a-b;printf("%d\n",c);break;}
                     ^
prog.c:16:9: error: stray '\357' in program
         case '*'：{c=a*b;printf("%d\n",c);break;}
         ^
prog.c:16:9: error: stray '\274' in program
prog.c:16:9: error: stray '\232' in program
prog.c:16:20: error: expected ':' or '...' before '{' token
         case '*'：{c=a*b;printf("%d\n",c);break;}
                    ^
prog.c:17:9: error: stray '\357' in program
         case '/'：{c=a/b;printf("%d\n",c);break;}
         ^
prog.c:17:9: error: stray '\274' in program
prog.c:17:9: error: stray '\232' in program
prog.c:17:20: error: expected ':' or '...' before '{' token
         case '/'：{c=a/b;printf("%d\n",c);break;}

说得很清楚了，你写的是 中文：，而应该是 英文:

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

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