Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:11:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<m[x].size();++i) { ^ user.cpp:10:9: warning: unused variable ‘ret’ [-Wunused-variable] int ret = 0; ^ user.cpp: In function ‘int main()’: user.cpp:34:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.in","r",stdin); ^ user.cpp:35:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.out","w",stdout); ^ user.cpp:37:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&T); ^ user.cpp:40:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&N,&M); ^ user.cpp:42:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^