Compilare: main.cpp: In function 'int longest_prefix(std::__cxx11::string, std::__cxx11::string)': main.cpp:13:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(a[idx] == b[idx] && idx < a.size() && idx < b.size()) { ~~~~^~~~~~~~~~ main.cpp:13:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(a[idx] == b[idx] && idx < a.size() && idx < b.size()) { ~~~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:21:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ratina.in","r",stdin); ^ main.cpp:22:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ratina.out","w",stdout); ^