Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:24:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<ar[s].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:35:32: 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); ^ user.cpp:36:34: 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); ^ user.cpp:48:11: warning: ‘s’ may be used uninitialized in this function [-Wmaybe-uninitialized] dfs(s); ^