Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:13:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<v[nod].size(); i++) ^ user.cpp:21:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == v[nod].size()) ^ user.cpp:30:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<v[nod].size(); j++) ^ user.cpp: In function ‘int main()’: user.cpp:49:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alpin.in","r",stdin); ^ user.cpp:50:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alpin.out","w",stdout); ^ user.cpp:51:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^ user.cpp:55:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&a[i][j]); ^