Compilare: user.cpp: In function ‘void df(int)’: user.cpp:14:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<a[i].size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:20:11: warning: unused variable ‘j’ [-Wunused-variable] int i,j,m,x,y; ^ user.cpp:21:32: 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:22:34: 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:23:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:26:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^