使用STL中的map时候，有时候需要使用结构题自定义键值，比如想统计点的坐标出现的次数
struct Node{
int x,y;
};
......
map<Node,int>mp;
mp[(Node){x,y}]++;
这样子的话，会出现一堆报错
c:mingwlibgccmingw324.8.1includec++itsstl_function.h||In instantiation of 'bool std::less<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = Node]':| c:mingwlibgccmingw324.8.1includec++itsstl_map.h|483|required from 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](std::map<_Key, _Tp, _Compare, _Alloc>::key_type&&) [with _Key = Node; _Tp = int; _Compare = std::less<Node>; _Alloc = std::allocator<std::pair<const Node, int> >; std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type = int; std::map<_Key, _Tp, _Compare, _Alloc>::key_type = Node]'| E:Programming Designpracticeceshi.cpp|27|required from here| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|error: no match for 'operator<' (operand types are 'const Node' and 'const Node')| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: candidates are:| c:mingwlibgccmingw324.8.1includec++itsstl_pair.h|220|note: template<class _T1, class _T2> constexpr bool std::operator<(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)| c:mingwlibgccmingw324.8.1includec++itsstl_pair.h|220|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::pair<_T1, _T2>'| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|297|note: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|297|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::reverse_iterator<_Iterator>'| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|347|note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|347|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::reverse_iterator<_Iterator>'| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|1055|note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::move_iterator<_Iterator>&, const std::move_iterator<_IteratorR>&)| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|1055|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::move_iterator<_Iterator>'| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|1061|note: template<class _Iterator> bool std::operator<(const std::move_iterator<_Iterator>&, const std::move_iterator<_Iterator>&)| c:mingwlibgccmingw324.8.1includec++itsstl_iterator.h|1061|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::move_iterator<_Iterator>'| c:mingwlibgccmingw324.8.1includec++itsasic_string.h|2569|note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsasic_string.h|2569|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::basic_string<_CharT, _Traits, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsasic_string.h|2581|note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)| c:mingwlibgccmingw324.8.1includec++itsasic_string.h|2581|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::basic_string<_CharT, _Traits, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsasic_string.h|2593|note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsasic_string.h|2593|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: mismatched types 'const _CharT*' and 'Node'| c:mingwlibgccmingw324.8.1includec++itsstl_vector.h|1420|note: template<class _Tp, class _Alloc> bool std::operator<(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_vector.h|1420|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::vector<_Tp, _Alloc>'| c:mingwlibgccmingw324.8.1includec++array|238|note: template<class _Tp, unsigned int _Nm> bool std::operator<(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)| c:mingwlibgccmingw324.8.1includec++array|238|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::array<_Tp, _Nm>'| c:mingwlibgccmingw324.8.1includec++ uple|822|note: template<class ... _TElements, class ... _UElements> constexpr bool std::operator<(const std::tuple<_Elements ...>&, const std::tuple<_Elements ...>&)| c:mingwlibgccmingw324.8.1includec++ uple|822|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::tuple<_Elements ...>'| c:mingwlibgccmingw324.8.1includec++itsstl_deque.h|273|note: template<class _Tp, class _Ref, class _Ptr> bool std::operator<(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _Ref, _Ptr>&)| c:mingwlibgccmingw324.8.1includec++itsstl_deque.h|273|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Deque_iterator<_Tp, _Ref, _Ptr>'| c:mingwlibgccmingw324.8.1includec++itsstl_deque.h|281|note: template<class _Tp, class _RefL, class _PtrL, class _RefR, class _PtrR> bool std::operator<(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _RefR, _PtrR>&)| c:mingwlibgccmingw324.8.1includec++itsstl_deque.h|281|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Deque_iterator<_Tp, _Ref, _Ptr>'| c:mingwlibgccmingw324.8.1includec++itsstl_deque.h|1975|note: template<class _Tp, class _Alloc> bool std::operator<(const std::deque<_Tp, _Alloc>&, const std::deque<_Tp, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_deque.h|1975|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::deque<_Tp, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsstl_list.h|1631|note: template<class _Tp, class _Alloc> bool std::operator<(const std::list<_Tp, _Alloc>&, const std::list<_Tp, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_list.h|1631|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::list<_Tp, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsstl_tree.h|914|note: template<class _Key, class _Val, class _KeyOfValue, class _Compare, class _Alloc> bool std::operator<(const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&, const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_tree.h|914|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsstl_map.h|978|note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const std::map<_Key, _Tp, _Compare, _Alloc>&, const std::map<_Key, _Tp, _Compare, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_map.h|978|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::map<_Key, _Tp, _Compare, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsstl_multimap.h|880|note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const std::multimap<_Key, _Tp, _Compare, _Alloc>&, const std::multimap<_Key, _Tp, _Compare, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_multimap.h|880|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::multimap<_Key, _Tp, _Compare, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsunique_ptr.h|523|note: template<class _Tp, class _Dp, class _Up, class _Ep> bool std::operator<(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)| c:mingwlibgccmingw324.8.1includec++itsunique_ptr.h|523|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::unique_ptr<_Tp, _Dp>'| c:mingwlibgccmingw324.8.1includec++itsunique_ptr.h|534|note: template<class _Tp, class _Dp> bool std::operator<(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)| c:mingwlibgccmingw324.8.1includec++itsunique_ptr.h|534|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::unique_ptr<_Tp, _Dp>'| c:mingwlibgccmingw324.8.1includec++itsunique_ptr.h|540|note: template<class _Tp, class _Dp> bool std::operator<(std::nullptr_t, const std::unique_ptr<_Tp, _Dp>&)| c:mingwlibgccmingw324.8.1includec++itsunique_ptr.h|540|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: cannot convert '__x' (type 'const Node') to type 'std::nullptr_t'| c:mingwlibgccmingw324.8.1includec++itsshared_ptr_base.h|1090|note: template<class _Tp1, class _Tp2, __gnu_cxx::_Lock_policy _Lp> bool std::operator<(const std::__shared_ptr<_Tp1, _Lp>&, const std::__shared_ptr<_Tp2, _Lp>&)| c:mingwlibgccmingw324.8.1includec++itsshared_ptr_base.h|1090|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::__shared_ptr<_Tp1, _Lp>'| c:mingwlibgccmingw324.8.1includec++itsshared_ptr_base.h|1099|note: template<class _Tp, __gnu_cxx::_Lock_policy _Lp> bool std::operator<(const std::__shared_ptr<_Tp, _Lp>&, std::nullptr_t)| c:mingwlibgccmingw324.8.1includec++itsshared_ptr_base.h|1099|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::__shared_ptr<_Tp, _Lp>'| c:mingwlibgccmingw324.8.1includec++itsshared_ptr_base.h|1104|note: template<class _Tp, __gnu_cxx::_Lock_policy _Lp> bool std::operator<(std::nullptr_t, const std::__shared_ptr<_Tp, _Lp>&)| c:mingwlibgccmingw324.8.1includec++itsshared_ptr_base.h|1104|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: cannot convert '__x' (type 'const Node') to type 'std::nullptr_t'| c:mingwlibgccmingw324.8.1includec++itsshared_ptr.h|359|note: template<class _Tp1, class _Tp2> bool std::operator<(const std::shared_ptr<_Tp1>&, const std::shared_ptr<_Tp2>&)| c:mingwlibgccmingw324.8.1includec++itsshared_ptr.h|359|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::shared_ptr<_Tp1>'| c:mingwlibgccmingw324.8.1includec++itsshared_ptr.h|368|note: template<class _Tp> bool std::operator<(const std::shared_ptr<_Tp1>&, std::nullptr_t)| c:mingwlibgccmingw324.8.1includec++itsshared_ptr.h|368|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::shared_ptr<_Tp1>'| c:mingwlibgccmingw324.8.1includec++itsshared_ptr.h|373|note: template<class _Tp> bool std::operator<(std::nullptr_t, const std::shared_ptr<_Tp1>&)| c:mingwlibgccmingw324.8.1includec++itsshared_ptr.h|373|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: cannot convert '__x' (type 'const Node') to type 'std::nullptr_t'| c:mingwlibgccmingw324.8.1includec++itsstl_queue.h|286|note: template<class _Tp, class _Seq> bool std::operator<(const std::queue<_Tp, _Seq>&, const std::queue<_Tp, _Seq>&)| c:mingwlibgccmingw324.8.1includec++itsstl_queue.h|286|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::queue<_Tp, _Seq>'| c:mingwlibgccmingw324.8.1includec++itsstl_set.h|769|note: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::set<_Key, _Compare, _Alloc>&, const std::set<_Key, _Compare, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_set.h|769|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::set<_Key, _Compare, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsstl_multiset.h|754|note: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::multiset<_Key, _Compare, _Alloc>&, const std::multiset<_Key, _Compare, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsstl_multiset.h|754|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::multiset<_Key, _Compare, _Alloc>'| c:mingwlibgccmingw324.8.1includec++itsstl_stack.h|261|note: template<class _Tp, class _Seq> bool std::operator<(const std::stack<_Tp, _Seq>&, const std::stack<_Tp, _Seq>&)| c:mingwlibgccmingw324.8.1includec++itsstl_stack.h|261|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::stack<_Tp, _Seq>'| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template<class _Dom1, class _Dom2> std::_Expr<std::_BinClos<std::__less, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::_Expr<_Dom2, typename _Dom2::value_type>&)| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const typename _Dom::value_type&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::valarray<typename _Dom::value_type>&)| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template<class _Dom> std::_Expr<std::_BinClos<std::__less, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__less, typename _Dom1::value_type>::result_type> std::operator<(const std::valarray<typename _Dom::value_type>&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)| c:mingwlibgccmingw324.8.1includec++itsvalarray_after.h|416|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::valarray<typename _Dom::value_type>'| c:mingwlibgccmingw324.8.1includec++valarray|1168|note: template<class _Tp> std::_Expr<std::_BinClos<std::__less, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__less, _Tp>::result_type> std::operator<(const std::valarray<_Tp>&, const std::valarray<_Tp>&)| c:mingwlibgccmingw324.8.1includec++valarray|1168|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::valarray<_Tp>'| c:mingwlibgccmingw324.8.1includec++valarray|1168|note: template<class _Tp> std::_Expr<std::_BinClos<std::__less, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__less, _Tp>::result_type> std::operator<(const std::valarray<_Tp>&, const _Tp&)| c:mingwlibgccmingw324.8.1includec++valarray|1168|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::valarray<_Tp>'| c:mingwlibgccmingw324.8.1includec++valarray|1168|note: template<class _Tp> std::_Expr<std::_BinClos<std::__less, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__less, _Tp>::result_type> std::operator<(const _Tp&, const std::valarray<_Tp>&)| c:mingwlibgccmingw324.8.1includec++valarray|1168|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::valarray<_Tp>'| c:mingwlibgccmingw324.8.1includec++system_error|177|note: bool std::operator<(const std::error_code&, const std::error_code&)| c:mingwlibgccmingw324.8.1includec++system_error|177|note: no known conversion for argument 1 from 'const Node' to 'const std::error_code&'| c:mingwlibgccmingw324.8.1includec++system_error|250|note: bool std::operator<(const std::error_condition&, const std::error_condition&)| c:mingwlibgccmingw324.8.1includec++system_error|250|note: no known conversion for argument 1 from 'const Node' to 'const std::error_condition&'| c:mingwlibgccmingw324.8.1includec++itsforward_list.h|1359|note: template<class _Tp, class _Alloc> bool std::operator<(const std::forward_list<_Tp, _Alloc>&, const std::forward_list<_Tp, _Alloc>&)| c:mingwlibgccmingw324.8.1includec++itsforward_list.h|1359|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::forward_list<_Tp, _Alloc>'| c:mingwlibgccmingw324.8.1includec++its egex.h|879|note: template<class _BiIter> bool std::operator<(const std::sub_match<_BiIter>&, const std::sub_match<_BiIter>&)| c:mingwlibgccmingw324.8.1includec++its egex.h|879|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::sub_match<_BiIter>'| c:mingwlibgccmingw324.8.1includec++its egex.h|955|note: template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::operator<(std::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::sub_match<_BiIter>&)| c:mingwlibgccmingw324.8.1includec++its egex.h|955|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'std::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'| c:mingwlibgccmingw324.8.1includec++its egex.h|1029|note: template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::operator<(const std::sub_match<_BiIter>&, std::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)| c:mingwlibgccmingw324.8.1includec++its egex.h|1029|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::sub_match<_BiIter>'| c:mingwlibgccmingw324.8.1includec++its egex.h|1103|note: template<class _Bi_iter> bool std::operator<(const typename std::iterator_traits<_Iter>::value_type*, const std::sub_match<_BiIter>&)| c:mingwlibgccmingw324.8.1includec++its egex.h|1103|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: mismatched types 'const typename std::iterator_traits<_Iter>::value_type*' and 'Node'| c:mingwlibgccmingw324.8.1includec++its egex.h|1177|note: template<class _Bi_iter> bool std::operator<(const std::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)| c:mingwlibgccmingw324.8.1includec++its egex.h|1177|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::sub_match<_BiIter>'| c:mingwlibgccmingw324.8.1includec++its egex.h|1254|note: template<class _Bi_iter> bool std::operator<(const typename std::iterator_traits<_Iter>::value_type&, const std::sub_match<_BiIter>&)| c:mingwlibgccmingw324.8.1includec++its egex.h|1254|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::sub_match<_BiIter>'| c:mingwlibgccmingw324.8.1includec++its egex.h|1334|note: template<class _Bi_iter> bool std::operator<(const std::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)| c:mingwlibgccmingw324.8.1includec++its egex.h|1334|note: template argument deduction/substitution failed:| c:mingwlibgccmingw324.8.1includec++itsstl_function.h|235|note: 'const Node' is not derived from 'const std::sub_match<_BiIter>'| ||=== Build failed: 1 error(s), 3 warning(s) (0 minute(s), 4 second(s)) ===|
看着似乎满屏错误，其实就是少了一个键值比较函数，因为我们知道map插入键值后默认从小到大排序，使用自定义结构体作为键值，但是没有自定义比较函数的话，编译器无法为插入的元素排序。
struct Node{
int x,y;
bool operator < (const Node &a)const
{
if (x == a.x) return y < a.y;
else return x < a.x;
}
};
这样子修改后，就可以成功运行了。其实从这个例子，我们可以类比用结构体自定义优先队列，也是需要自写比较函数的。