foo.cc: In function 'void add(int, int, int)':
foo.cc:22:43: error: reference to 'next' is ambiguous
     tot++; to[ tot ] = y , w[ tot ] = z , next[ tot ] = head[ x ] , head[ x ] = tot;
                                           ^~~~
foo.cc:6:60: note: candidates are: int next [800380]
 int  head[ N*2 ] , d[ N*2 ] , to[ N*10*2 ] , w[ N*10*2 ] , next[ N*10*2 ]  ;
                                                            ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
foo.cc:23:43: error: reference to 'next' is ambiguous
     tot++; to[ tot ] = x , w[ tot ] = 0 , next[ tot ] = head[ y ] , head[ y ] = tot;
                                           ^~~~
foo.cc:6:60: note: candidates are: int next [800380]
 int  head[ N*2 ] , d[ N*2 ] , to[ N*10*2 ] , w[ N*10*2 ] , next[ N*10*2 ]  ;
                                                            ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
foo.cc: In function 'bool bfs()':
foo.cc:32:43: error: reference to 'next' is ambiguous
         for( int  i = head[ x ] ; i ; i = next[ i ])
                                           ^~~~
foo.cc:6:60: note: candidates are: int next [800380]
 int  head[ N*2 ] , d[ N*2 ] , to[ N*10*2 ] , w[ N*10*2 ] , next[ N*10*2 ]  ;
                                                            ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
foo.cc: In function 'int dinic(int, int)':
foo.cc:45:47: error: reference to 'next' is ambiguous
     for( int  i = head[ x ] ; i && rest ; i = next[ i ] )//当前可流入最大流量不为0 ,
                                               ^~~~
foo.cc:6:60: note: candidates are: int next [800380]
 int  head[ N*2 ] , d[ N*2 ] , to[ N*10*2 ] , w[ N*10*2 ] , next[ N*10*2 ]  ;
                                                            ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
foo.cc: In function 'void clear()':
foo.cc:59:40: error: reference to 'next' is ambiguous
         w[ i ] = to[ i ] = head[ i ] = next[ i ] = 0 ;
                                        ^~~~
foo.cc:6:60: note: candidates are: int next [800380]
 int  head[ N*2 ] , d[ N*2 ] , to[ N*10*2 ] , w[ N*10*2 ] , next[ N*10*2 ]  ;
                                                            ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/c++/7/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:208:5: note:                 template<class _ForwardIterator> _ForwardIterator std::next(_ForwardIterator, typename std::iterator_traits<_Iter>::difference_type)
     next(_ForwardIterator __x, typename
     ^~~~
foo.cc: In function 'int main()':
foo.cc:81:25: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
             while( flow = dinic ( s , inf ))maxflow += flow ; 
                    ~~~~~^~~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。