Compilare: user.cpp: In function ‘int nr_elem(std::string)’: user.cpp:18:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<s.size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:59:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();++i) ^ user.cpp:67:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();++i){ ^ user.cpp:53:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("input.txt","r",stdin); ^ user.cpp: In function ‘int nr_elem(std::string)’: user.cpp:32:10: warning: ‘nrelem’ may be used uninitialized in this function [-Wmaybe-uninitialized] return nrelem; ^