Compilare: main.cpp: In function 'void dfs(int, std::vector<std::vector<int> >)': main.cpp:10:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < adj[i].size(); j++) ~~^~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:18:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.in", "r", stdin); ^ main.cpp:19:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.out", "w", stdout); ^