Compilare: main.cpp: In function 'int main()': main.cpp:9:24: warning: passing NULL to non-pointer argument 2 of 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::getline(std::basic_istream<_CharT, _Traits>::char_type*, std::streamsize) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::char_type = char; std::streamsize = long int]' [-Wconversion-null] fin.getline(s1,NULL); ^ main.cpp:10:24: warning: passing NULL to non-pointer argument 2 of 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::getline(std::basic_istream<_CharT, _Traits>::char_type*, std::streamsize) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::char_type = char; std::streamsize = long int]' [-Wconversion-null] fin.getline(s2,NULL); ^ main.cpp:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<strlen(s1);i++) ~^~~~~~~~~~~ main.cpp:21:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(s2);i++) ~^~~~~~~~~~~ main.cpp:28:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j==strlen(s1)) ~^~~~~~~~~~~~