这是我尝试做的事情：
#include <iostream>
#include <set>
#include <algorithm>
using namespace std;
struct node{
int x;
int y;
};
multiset<node> mset;
int main() {
node b=node();
b={1,2};
mset.insert({1,2});
mset.erase(b);
cout<<mset.size()<<endl;
cout<<b.y;
return 0;
}
它似乎不起作用。它给出了以下编译错误，我无法理解。
我已经完成了一个关于从多个结构中删除元素的线程，但它似乎也没有帮助。
编辑： 因为人们抱怨这里是错误：
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h: In instantiation of ‘constexpr bool std::less<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = node]’:
/usr/include/c++/6/bits/stl_tree.h:1867:51: required from ‘std::pair<std::_Rb_tree_node_base*, std::_Rb_tree_node_base*> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_get_insert_equal_pos(const key_type&) [with _Key = node; _Val = node; _KeyOfValue = std::_Identity<node>; _Compare = std::less<node>; _Alloc = std::allocator<node>; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::key_type = node]’
/usr/include/c++/6/bits/stl_tree.h:1916:27: required from ‘std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_equal(_Arg&&) [with _Arg = node; _Key = node; _Val = node; _KeyOfValue = std::_Identity<node>; _Compare = std::less<node>; _Alloc = std::allocator<node>; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator = std::_Rb_tree_iterator<node>]’
/usr/include/c++/6/bits/stl_multiset.h:479:51: required from ‘std::multiset<_Key, _Compare, _Alloc>::iterator std::multiset<_Key, _Compare, _Alloc>::insert(std::multiset<_Key, _Compare, _Alloc>::value_type&&) [with _Key = node; _Compare = std::less<node>; _Alloc = std::allocator<node>; std::multiset<_Key, _Compare, _Alloc>::iterator = std::_Rb_tree_const_iterator<node>; std::multiset<_Key, _Compare, _Alloc>::value_type = node]’
prog.cpp:13:19: required from here
/usr/include/c++/6/bits/stl_function.h:386:20: error: no match for ‘operator<’ (operand types are ‘const node’ and ‘const node’)
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:64:0,
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 prog.cpp:1:
/usr/include/c++/6/bits/stl_pair.h:437:5: note: candidate: template<class _T1, class _T2> constexpr bool std::operator<(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
^~~~~~~~
/usr/include/c++/6/bits/stl_pair.h:437:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::pair<_T1, _T2>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:67:0,
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 prog.cpp:1:
/usr/include/c++/6/bits/stl_iterator.h:298:5: note: candidate: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
operator<(const reverse_iterator<_Iterator>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_iterator.h:298:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::reverse_iterator<_Iterator>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:67:0,
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 prog.cpp:1:
/usr/include/c++/6/bits/stl_iterator.h:355:5: note: candidate: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)
operator<(const reverse_iterator<_IteratorL>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_iterator.h:355:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::reverse_iterator<_Iterator>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:67:0,
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 prog.cpp:1:
/usr/include/c++/6/bits/stl_iterator.h:1137:5: note: candidate: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)
operator<(const move_iterator<_IteratorL>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_iterator.h:1137:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::move_iterator<_IteratorL>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:67:0,
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 prog.cpp:1:
/usr/include/c++/6/bits/stl_iterator.h:1143:5: note: candidate: template<class _Iterator> bool std::operator<(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)
operator<(const move_iterator<_Iterator>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_iterator.h:1143:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::move_iterator<_IteratorL>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/string:52:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/basic_string.h:5150:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
^~~~~~~~
/usr/include/c++/6/bits/basic_string.h:5150:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/string:52:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/basic_string.h:5163:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
^~~~~~~~
/usr/include/c++/6/bits/basic_string.h:5163:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/string:52:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/basic_string.h:5175:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
operator<(const _CharT* __lhs,
^~~~~~~~
/usr/include/c++/6/bits/basic_string.h:5175:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: mismatched types ‘const _CharT*’ and ‘node’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/bits/ios_base.h:46:0,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/system_error:200:3: note: candidate: bool std::operator<(const std::error_code&, const std::error_code&)
operator<(const error_code& __lhs, const error_code& __rhs) noexcept
^~~~~~~~
/usr/include/c++/6/system_error:200:3: note: no known conversion for argument 1 from ‘const node’ to ‘const std::error_code&’
/usr/include/c++/6/system_error:274:3: note: candidate: bool std::operator<(const std::error_condition&, const std::error_condition&)
operator<(const error_condition& __lhs,
^~~~~~~~
/usr/include/c++/6/system_error:274:3: note: no known conversion for argument 1 from ‘const node’ to ‘const std::error_condition&’
In file included from /usr/include/c++/6/set:60:0,
from prog.cpp:2:
/usr/include/c++/6/bits/stl_tree.h:1292:5: note: candidate: 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>&)
operator<(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_tree.h:1292:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/set:61:0,
from prog.cpp:2:
/usr/include/c++/6/bits/stl_set.h:857:5: note: candidate: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::set<_Key, _Compare, _Alloc>&, const std::set<_Key, _Compare, _Alloc>&)
operator<(const set<_Key, _Compare, _Alloc>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_set.h:857:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::set<_Key, _Compare, _Alloc>’
{ return __x < __y; }
~~~~^~~~~
In file included from /usr/include/c++/6/set:62:0,
from prog.cpp:2:
/usr/include/c++/6/bits/stl_multiset.h:840:5: note: candidate: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::multiset<_Key, _Compare, _Alloc>&, const std::multiset<_Key, _Compare, _Alloc>&)
operator<(const multiset<_Key, _Compare, _Alloc>& __x,
^~~~~~~~
/usr/include/c++/6/bits/stl_multiset.h:840:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/6/string:48:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from prog.cpp:1:
/usr/include/c++/6/bits/stl_function.h:386:20: note: ‘const node’ is not derived from ‘const std::multiset<_Key, _Compare, _Alloc>’
{ return __x < __y; }
~~~~^~~~~
编辑： 它工作，我只需要添加一个布尔运算符＆lt;比较两个节点。
已编辑了ideone链接。
答案 0 :(得分：4)
编译器错误表明没有bool operator<(node, node)。实施一个。 E.g：
#include <tuple>
inline bool operator<(node const& a, node const& b) {
return std::tie(a.x, a.y) < std::tie(b.x, b.y);
}
答案 1 :(得分：-2)
您错过了关联容器所需的比较器。添加
bool operator<(const node& a, const node& b)
{
return a.x < b.x ? true : (a.x == b.x ? a.y < b.y : false);
}