Compilare: main.cpp: In function 'void join_all(int, int)': main.cpp:82:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (gr[node].size () != degree[node]) ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:102:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("metrou2.in", "r", stdin); ^ main.cpp:103:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("metrou2.out", "w", stdout); ^