/in/foo.cc: In function 'void bfs()':
/in/foo.cc:25:14: error: expected unqualified-id before '[' token
         auto [current_state, step] = q.front();
              ^
/in/foo.cc:29:13: error: 'current_state' was not declared in this scope
         if (current_state == target) {
             ^~~~~~~~~~~~~
/in/foo.cc:30:21: error: 'step' was not declared in this scope
             cout << step << endl;
                     ^~~~
/in/foo.cc:36:30: error: 'current_state' was not declared in this scope
             int next_state = current_state;
                              ^~~~~~~~~~~~~
/in/foo.cc:48:37: error: 'step' was not declared in this scope
                 q.push({next_state, step + 1});
                                     ^~~~
/in/foo.cc:48:46: error: no matching function for call to 'std::queue<std::pair<int, int> >::push(<brace-enclosed initializer list>)'
                 q.push({next_state, step + 1});
                                              ^
In file included from /usr/include/c++/6/queue:64:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:86,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_queue.h:242:7: note: candidate: void std::queue<_Tp, _Sequence>::push(const value_type&) [with _Tp = std::pair<int, int>; _Sequence = std::deque<std::pair<int, int>, std::allocator<std::pair<int, int> > >; std::queue<_Tp, _Sequence>::value_type = std::pair<int, int>]
       push(const value_type& __x)
       ^~~~
/usr/include/c++/6/bits/stl_queue.h:242:7: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'const value_type& {aka const std::pair<int, int>&}'
/usr/include/c++/6/bits/stl_queue.h:247:7: note: candidate: void std::queue<_Tp, _Sequence>::push(std::queue<_Tp, _Sequence>::value_type&&) [with _Tp = std::pair<int, int>; _Sequence = std::deque<std::pair<int, int>, std::allocator<std::pair<int, int> > >; std::queue<_Tp, _Sequence>::value_type = std::pair<int, int>]
       push(value_type&& __x)
       ^~~~
/usr/include/c++/6/bits/stl_queue.h:247:7: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'std::queue<std::pair<int, int> >::value_type&& {aka std::pair<int, int>&&}'