/in/foo.cc: In function 'int main()':
/in/foo.cc:32:26: error: 'pointer' was not declared in this scope
   for (int j=head[i];j;j=pointer[j])
                          ^~~~~~~
/in/foo.cc:32:26: note: suggested alternative: 'printf'
   for (int j=head[i];j;j=pointer[j])
                          ^~~~~~~
                          printf