Compilare: main.cpp: In function 'void dfs(int, std::vector<bool>&, std::vector<int>*)': main.cpp:10:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0 ; i < adj[src].size() ; ++i) { ~~^~~~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:20:31: 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:21:33: 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); ^ main.cpp:22:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &N, &M); ^ main.cpp:30:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &src, &dest); ^