Compilare: main.cpp: In function 'int main()': main.cpp:57:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nfa.in", "r", stdin); ^ main.cpp:58:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nfa.out", "w", stdout); ^ main.cpp: In function 'bool check_nfa(std::__cxx11::string)': main.cpp:36:12: warning: 'end_state' may be used uninitialized in this function [-Wmaybe-uninitialized] return end_state; ^~~~~~~~~