/in/foo.cc: In member function 'bool prtcmp::operator()(const char*, const char*) const':
/in/foo.cc:17:22: error: 'strcmp' was not declared in this scope
   return strcmp(s1,s2)<0;
                      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:44:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(i=0;i<ans.size();i++)
            ~^~~~~~~~~~~