Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:16:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<a[x].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:31:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&n); ^ user.cpp:33:48: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (int i=1;i<=n;i++) fscanf(f,"%d",&v[i]); ^ user.cpp:38:31: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&x,&y); ^