foo.cc: In function 'int main()':
foo.cc:11:27: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'int*' [-Wformat=]
         scanf("%s",a[b[j]]);
                           ^
foo.cc:14:27: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'int*' [-Wformat=]
         printf("%s\n",a[j]);
                           ^
foo.cc:5:15: warning: unused variable 'k' [-Wunused-variable]
     int i=0,j,k;
               ^
foo.cc:8:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&b[i++]);
         ~~~~~^~~~~~~~~~~~~~
foo.cc:11:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%s",a[b[j]]);
         ~~~~~^~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。