/in/foo.c: In function 'main':
/in/foo.c:12:6: error: 'i' undeclared (first use in this function)
  for(i=0;i<=n;i++)
      ^
/in/foo.c:12:6: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:4:18: warning: variable 'arr' set but not used [-Wunused-but-set-variable]
  int xmin,xmax,n,arr[4],b[4],x,y;
                  ^~~
/in/foo.c: At top level:
/in/foo.c:44:12: error: expected declaration specifiers or '...' before string constant
     printf("出现次数最多的数字为:%d",b[x]);
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.c:44:48: error: unknown type name 'b'
     printf("出现次数最多的数字为:%d",b[x]);
                                                ^
/in/foo.c:47:1: error: expected identifier or '(' before '}' token
 }
 ^