Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:29:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1; i<=a[x].size()-1; i++) ^ user.cpp: In function ‘int main()’: user.cpp:40:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.in","rt",stdin); ^ user.cpp:41:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.out","wt",stdout); ^