/in/foo.cc: In constructor 'hnode::hnode()':
/in/foo.cc:18:6: warning: 'hnode::step' will be initialized after [-Wreorder]
  int step;
      ^~~~
/in/foo.cc:16:9: warning:   'std::__cxx11::string hnode::s' [-Wreorder]
  string s;
         ^
/in/foo.cc:19:2: warning:   when initialized here [-Wreorder]
  hnode():next(NULL),step(99),s(""){}
  ^~~~~
/in/foo.cc:19:34: warning: converting to non-pointer type 'int' from NULL [-Wconversion-null]
  hnode():next(NULL),step(99),s(""){}
                                  ^
/in/foo.cc: In function 'int add_node(std::__cxx11::string)':
/in/foo.cc:85:22: warning: NULL used in arithmetic [-Wpointer-arith]
   if ( h[k]->next == NULL)
                      ^~~~
/in/foo.cc: In function 'bool search(std::__cxx11::string, std::__cxx11::string, int)':
/in/foo.cc:101:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while (j<s.length() && i<s1.length())
         ~^~~~~~~~~~~
/in/foo.cc:101:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while (j<s.length() && i<s1.length())
                         ~^~~~~~~~~~~~
/in/foo.cc:107:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (i<s1.length()) return false;
      ~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:140:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(j=0; j<s1.length(); ++j)
             ~^~~~~~~~~~~~