/in/foo.cc: In function 'void add(int, int, int)':
/in/foo.cc:13:2: error: reference to 'next' is ambiguous
  next[tot]=head[x];
  ^~~~
/in/foo.cc:8:30: note: candidates are: int next [500005]
 int head[100005],ver[500005],next[500005],d[100005],f[100005];
                              ^~~~
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:18:3: error: reference to 'next' is ambiguous
   next[tot]=head[y];
   ^~~~
/in/foo.cc:8:30: note: candidates are: int next [500005]
 int head[100005],ver[500005],next[500005],d[100005],f[100005];
                              ^~~~
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 spfa1()':
/in/foo.cc:32:25: error: reference to 'next' is ambiguous
   for(int i=head[x];i;i=next[i])
                         ^~~~
/in/foo.cc:8:30: note: candidates are: int next [500005]
 int head[100005],ver[500005],next[500005],d[100005],f[100005];
                              ^~~~
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 spfa2()':
/in/foo.cc:53:25: error: reference to 'next' is ambiguous
   for(int i=head[x];i;i=next[i])
                         ^~~~
/in/foo.cc:8:30: note: candidates are: int next [500005]
 int head[100005],ver[500005],next[500005],d[100005],f[100005];
                              ^~~~
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
     ^~~~