/in/foo.cc: In function 'void add(int, int)':
/in/foo.cc:19:3: error: reference to 'next' is ambiguous
   next[++cnt]=point[x];point[x]=cnt;
   ^~~~
/in/foo.cc:7:20: note: candidates are: int next [200020]
 int n,m,T,point[N],next[N<<1],cnt,q[N],h,t,x,y,fa[N];
                    ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_iterator_base_funcs.h:205:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
/in/foo.cc: In function 'void bfs(int)':
/in/foo.cc:36:25: error: reference to 'next' is ambiguous
  for(int i=point[u];i;i=next[i])
                         ^~~~
/in/foo.cc:7:20: note: candidates are: int next [200020]
 int n,m,T,point[N],next[N<<1],cnt,q[N],h,t,x,y,fa[N];
                    ^~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_iterator_base_funcs.h:205:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~