Compilare: user.cpp: In function ‘void dfs(int, int)’: user.cpp:23:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<g[u].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:31:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("playlist.in","r",stdin); ^ user.cpp:32:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("playlist.out","w",stdout); ^ user.cpp:34:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:36:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^