Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:10:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[x].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:33:15: warning: statement has no effect [-Wunused-value] {vec[i]; ^ user.cpp:15:30: 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:16:31: 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:18:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:20:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] {scanf("%d%d",&x,&y); ^