Submission #1278826

#TimeUsernameProblemLanguageResultExecution timeMemory
1278826janson0109Bridges (APIO19_bridges)C++20
Compilation error
0 ms0 KiB
#include <bits/stdc++.h> #define F first #define S second #define lol ios::sync_with_stdio(false);cin.tie(NULL); typedef int ll; typedef long double ld; using namespace std; const ll M = 998244353; #define p3 tuple<ll,ll,ll> #define p4 tuple<ll,ll,ll,ll> ll find(ll x, vector<ll> &p, vector<pair<ll,ll>> &ph, bool his) { if(p[x] == x) return x; //if(his) ph.push_back({x, p[x]}); return find(p[x], p, ph, his); //return p[x]; } bool unite(ll x, ll y, vector<ll> &p, vector<ll> &s, vector<pair<ll,ll>> &ph, vector<pair<ll,ll>> &sh, bool his) { ll xr = find(x, p, ph, his); ll yr = find(y, p, ph, his); if(xr == yr) return false; if(s[xr] < s[yr]) swap(xr,yr); if(his) { sh.push_back({xr, s[xr]}); ph.push_back({yr, p[yr]}); } s[xr]+=s[yr]; p[yr]=xr; return true; } void rollback(vector<ll> &p, vector<ll> &s, vector<pair<ll,ll>> &ph, vector<pair<ll,ll>> &sh) { while(!ph.empty()) { pair<ll,ll> pa = ph.back(); p[pa.F] = pa.S; ph.pop_back(); } while(!sh.empty()) { pair<ll,ll> pa = sh.back(); s[pa.F] = pa.S; sh.pop_back(); } } int main() { lol ll n, m; cin >> n >> m; vector<p3> e; set<p4, greater<p4>> es; for(ll i=0; i<m; i++) { ll u, v, d; cin >> u >> v >> d; u--;v--; e.push_back({d, u, v}); es.insert({d, u, v, i}); } ll q; cin >> q; vector<p3> qu(q); for(ll i=0; i<q; i++) cin >> get<0>(qu[i]) >> get<1>(qu[i]) >> get<2>(qu[i]); ll b = sqrtl(q); for(ll t=0; t < q; t+=b) { ll c = min(b, q-t); vector<bool> ch(m,0); for(ll i=0; i<c; i++) if(get<0>(qu[t+i]) == 1) ch[get<1>(qu[t+i]) - 1] = 1; vector<ll> mod; set<p3> mods; for(ll i=0; i<m; i++) if(ch[i]) {mod.push_back(i); mods.insert(e[i]);} ll k = mod.size(); vector<ll> modm(m, -1); vector<ll> nd(k); for(ll i=0; i<k; i++) { nd[i] = get<0>(e[mod[i]]); modm[mod[i]] = i; } vector<vector<ll>> ndm(c); for(ll i=0; i<c; i++) { if(get<0>(qu[t+i]) == 1) nd[modm[get<1>(qu[t+i]) - 1]] = get<2>(qu[t+i]); else ndm[i] = nd; } vector<p3> qus; for(ll i=0; i<c; i++) if(get<0>(qu[t+i]) == 2) qus.push_back({get<2>(qu[t+i]), get<1>(qu[t+i])-1, i}); sort(qus.begin(), qus.end(), greater<p3>()); vector<ll> p(n), s(n,1); iota(p.begin(), p.end(), 0); vector<ll> ans(c, -1); vector<pair<ll,ll>> ph, sh; vector<p3> uc; for(auto & x : es) if(mods.find(x) == mods.end()) uc.push_back(x); auto it = uc.begin(); for(auto & quer : qus) { while(it != uc.end() && get<0>(quer) <= get<0>(*it)) { unite(get<1>(*it), get<2>(*it), p, s, ph, sh, 0); it++; } for(ll j=0; j<k; j++) if(get<0>(quer) <= ndm[get<2>(quer)][j]) unite(get<1>(e[mod[j]]), get<2>(e[mod[j]]), p, s, ph, sh, 1); ans[get<2>(quer)] = s[find(get<1>(quer), p, ph, 1)]; rollback(p, s, ph, sh); } for(ll i=0; i<c; i++) if(get<0>(qu[t+i]) == 1) { ll j = get<1>(qu[t+i]) - 1; es.erase({get<0>(e[j]), get<1>(e[j]), get<2>(e[j]), j}); get<0>(e[j]) = get<2>(qu[t+i]); es.insert({get<0>(e[j]), get<1>(e[j]), get<2>(e[j]), j}); if(e.size() != es.size()) cout << get<0>(e[1e9]) << '\n'; } for(ll i=0; i<c; i++) if(ans[i] != -1) cout << ans[i] << '\n'; } return 0; }

Compilation message (stderr)

bridges.cpp: In function 'int main()':
bridges.cpp:88:40: error: no matching function for call to 'std::set<std::tuple<int, int, int> >::find(const std::tuple<int, int, int, int>&)'
   88 |         for(auto & x : es) if(mods.find(x) == mods.end()) uc.push_back(x);
      |                               ~~~~~~~~~^~~
In file included from /usr/include/c++/13/set:63,
                 from /usr/include/x86_64-linux-gnu/c++/13/bits/stdc++.h:158,
                 from bridges.cpp:1:
/usr/include/c++/13/bits/stl_set.h:806:9: note: candidate: 'template<class _Kt> decltype (std::set<_Key, _Compare, _Alloc>::iterator{((std::set<_Key, _Compare, _Alloc>*)this)->std::set<_Key, _Compare, _Alloc>::_M_t._M_find_tr(__x)}) std::set<_Key, _Compare, _Alloc>::find(const _Kt&) [with _Key = std::tuple<int, int, int>; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >]'
  806 |         find(const _Kt& __x)
      |         ^~~~
/usr/include/c++/13/bits/stl_set.h:806:9: note:   template argument deduction/substitution failed:
/usr/include/c++/13/bits/stl_set.h: In substitution of 'template<class _Kt> decltype (std::set<std::tuple<int, int, int> >::iterator{((std::set<std::tuple<int, int, int> >*)this)->std::set<std::tuple<int, int, int> >::_M_t.std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::_M_find_tr(__x)}) std::set<std::tuple<int, int, int> >::find(const _Kt&) [with _Kt = std::tuple<int, int, int, int>]':
bridges.cpp:88:40:   required from here
/usr/include/c++/13/bits/stl_set.h:807:45: error: no matching function for call to 'std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::_M_find_tr(const std::tuple<int, int, int, int>&)'
  807 |         -> decltype(iterator{_M_t._M_find_tr(__x)})
      |                              ~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/13/map:62,
                 from /usr/include/x86_64-linux-gnu/c++/13/bits/stdc++.h:152:
/usr/include/c++/13/bits/stl_tree.h:1295:9: note: candidate: 'template<class _Kt, class _Req> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_find_tr(const _Kt&) [with _Req = _Kt; _Key = std::tuple<int, int, int>; _Val = std::tuple<int, int, int>; _KeyOfValue = std::_Identity<std::tuple<int, int, int> >; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >]'
 1295 |         _M_find_tr(const _Kt& __k)
      |         ^~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:1295:9: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/13/string:49,
                 from /usr/include/c++/13/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/13/bits/stdc++.h:52:
/usr/include/c++/13/bits/stl_function.h: In substitution of 'template<class _Func, class _SfinaeType> using std::__has_is_transparent_t = typename std::__has_is_transparent<_Func, _SfinaeType>::type [with _Func = std::less<std::tuple<int, int, int> >; _SfinaeType = std::tuple<int, int, int, int>]':
/usr/include/c++/13/bits/stl_tree.h:1293:9:   required by substitution of 'template<class _Kt> decltype (std::set<std::tuple<int, int, int> >::iterator{((std::set<std::tuple<int, int, int> >*)this)->std::set<std::tuple<int, int, int> >::_M_t.std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::_M_find_tr(__x)}) std::set<std::tuple<int, int, int> >::find(const _Kt&) [with _Kt = std::tuple<int, int, int, int>]'
bridges.cpp:88:40:   required from here
/usr/include/c++/13/bits/stl_function.h:1430:11: error: no type named 'type' in 'struct std::__has_is_transparent<std::less<std::tuple<int, int, int> >, std::tuple<int, int, int, int>, void>'
 1430 |     using __has_is_transparent_t
      |           ^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_set.h: In substitution of 'template<class _Kt> decltype (std::set<std::tuple<int, int, int> >::iterator{((std::set<std::tuple<int, int, int> >*)this)->std::set<std::tuple<int, int, int> >::_M_t.std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::_M_find_tr(__x)}) std::set<std::tuple<int, int, int> >::find(const _Kt&) [with _Kt = std::tuple<int, int, int, int>]':
bridges.cpp:88:40:   required from here
/usr/include/c++/13/bits/stl_tree.h:1304:9: note: candidate: 'template<class _Kt, class _Req> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::const_iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_find_tr(const _Kt&) const [with _Req = _Kt; _Key = std::tuple<int, int, int>; _Val = std::tuple<int, int, int>; _KeyOfValue = std::_Identity<std::tuple<int, int, int> >; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >]'
 1304 |         _M_find_tr(const _Kt& __k) const
      |         ^~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:1304:9: note:   template argument deduction/substitution failed:
/usr/include/c++/13/bits/stl_set.h:806:9: error: no matching function for call to 'std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::_Rb_tree_const_iterator(<brace-enclosed initializer list>)'
  806 |         find(const _Kt& __x)
      |         ^~~~
/usr/include/c++/13/bits/stl_tree.h:350:7: note: candidate: 'std::_Rb_tree_const_iterator<_Tp>::_Rb_tree_const_iterator(const iterator&) [with _Tp = std::tuple<int, int, int>; iterator = std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::iterator]'
  350 |       _Rb_tree_const_iterator(const iterator& __it) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:350:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_tree.h:347:7: note: candidate: 'std::_Rb_tree_const_iterator<_Tp>::_Rb_tree_const_iterator(_Base_ptr) [with _Tp = std::tuple<int, int, int>; _Base_ptr = const std::_Rb_tree_node_base*]'
  347 |       _Rb_tree_const_iterator(_Base_ptr __x) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:347:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_tree.h:343:7: note: candidate: 'std::_Rb_tree_const_iterator<_Tp>::_Rb_tree_const_iterator() [with _Tp = std::tuple<int, int, int>]'
  343 |       _Rb_tree_const_iterator() _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:343:7: note:   candidate expects 0 arguments, 1 provided
/usr/include/c++/13/bits/stl_tree.h:328:12: note: candidate: 'constexpr std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::_Rb_tree_const_iterator(const std::_Rb_tree_const_iterator<std::tuple<int, int, int> >&)'
  328 |     struct _Rb_tree_const_iterator
      |            ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:328:12: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_tree.h:328:12: note: candidate: 'constexpr std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::_Rb_tree_const_iterator(std::_Rb_tree_const_iterator<std::tuple<int, int, int> >&&)'
/usr/include/c++/13/bits/stl_tree.h:328:12: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_set.h:812:9: note: candidate: 'template<class _Kt> decltype (std::set<_Key, _Compare, _Alloc>::const_iterator{((const std::set<_Key, _Compare, _Alloc>*)this)->std::set<_Key, _Compare, _Alloc>::_M_t._M_find_tr(__x)}) std::set<_Key, _Compare, _Alloc>::find(const _Kt&) const [with _Key = std::tuple<int, int, int>; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >]'
  812 |         find(const _Kt& __x) const
      |         ^~~~
/usr/include/c++/13/bits/stl_set.h:812:9: note:   template argument deduction/substitution failed:
/usr/include/c++/13/bits/stl_set.h: In substitution of 'template<class _Kt> decltype (std::set<std::tuple<int, int, int> >::const_iterator{((const std::set<std::tuple<int, int, int> >*)this)->std::set<std::tuple<int, int, int> >::_M_t.std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::_M_find_tr(__x)}) std::set<std::tuple<int, int, int> >::find(const _Kt&) const [with _Kt = std::tuple<int, int, int, int>]':
bridges.cpp:88:40:   required from here
/usr/include/c++/13/bits/stl_set.h:813:51: error: no matching function for call to 'std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::_M_find_tr(const std::tuple<int, int, int, int>&) const'
  813 |         -> decltype(const_iterator{_M_t._M_find_tr(__x)})
      |                                    ~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/13/bits/stl_tree.h:1295:9: note: candidate: 'template<class _Kt, class _Req> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_find_tr(const _Kt&) [with _Req = _Kt; _Key = std::tuple<int, int, int>; _Val = std::tuple<int, int, int>; _KeyOfValue = std::_Identity<std::tuple<int, int, int> >; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >]'
 1295 |         _M_find_tr(const _Kt& __k)
      |         ^~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:1295:9: note:   template argument deduction/substitution failed:
/usr/include/c++/13/bits/stl_tree.h:1304:9: note: candidate: 'template<class _Kt, class _Req> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::const_iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_find_tr(const _Kt&) const [with _Req = _Kt; _Key = std::tuple<int, int, int>; _Val = std::tuple<int, int, int>; _KeyOfValue = std::_Identity<std::tuple<int, int, int> >; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >]'
 1304 |         _M_find_tr(const _Kt& __k) const
      |         ^~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:1304:9: note:   template argument deduction/substitution failed:
/usr/include/c++/13/bits/stl_set.h:812:9: error: no matching function for call to 'std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::_Rb_tree_const_iterator(<brace-enclosed initializer list>)'
  812 |         find(const _Kt& __x) const
      |         ^~~~
/usr/include/c++/13/bits/stl_tree.h:350:7: note: candidate: 'std::_Rb_tree_const_iterator<_Tp>::_Rb_tree_const_iterator(const iterator&) [with _Tp = std::tuple<int, int, int>; iterator = std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::iterator]'
  350 |       _Rb_tree_const_iterator(const iterator& __it) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:350:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_tree.h:347:7: note: candidate: 'std::_Rb_tree_const_iterator<_Tp>::_Rb_tree_const_iterator(_Base_ptr) [with _Tp = std::tuple<int, int, int>; _Base_ptr = const std::_Rb_tree_node_base*]'
  347 |       _Rb_tree_const_iterator(_Base_ptr __x) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:347:7: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_tree.h:343:7: note: candidate: 'std::_Rb_tree_const_iterator<_Tp>::_Rb_tree_const_iterator() [with _Tp = std::tuple<int, int, int>]'
  343 |       _Rb_tree_const_iterator() _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:343:7: note:   candidate expects 0 arguments, 1 provided
/usr/include/c++/13/bits/stl_tree.h:328:12: note: candidate: 'constexpr std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::_Rb_tree_const_iterator(const std::_Rb_tree_const_iterator<std::tuple<int, int, int> >&)'
  328 |     struct _Rb_tree_const_iterator
      |            ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/stl_tree.h:328:12: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_tree.h:328:12: note: candidate: 'constexpr std::_Rb_tree_const_iterator<std::tuple<int, int, int> >::_Rb_tree_const_iterator(std::_Rb_tree_const_iterator<std::tuple<int, int, int> >&&)'
/usr/include/c++/13/bits/stl_tree.h:328:12: note:   conversion of argument 1 would be ill-formed:
/usr/include/c++/13/bits/stl_set.h:796:7: note: candidate: 'std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::find(const key_type&) [with _Key = std::tuple<int, int, int>; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >; iterator = std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::const_iterator; key_type = std::tuple<int, int, int>]'
  796 |       find(const key_type& __x)
      |       ^~~~
/usr/include/c++/13/bits/stl_set.h:796:28: note:   no known conversion for argument 1 from 'const std::tuple<int, int, int, int>' to 'const std::set<std::tuple<int, int, int> >::key_type&' {aka 'const std::tuple<int, int, int>&'}
  796 |       find(const key_type& __x)
      |            ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/13/bits/stl_set.h:800:7: note: candidate: 'std::set<_Key, _Compare, _Alloc>::const_iterator std::set<_Key, _Compare, _Alloc>::find(const key_type&) const [with _Key = std::tuple<int, int, int>; _Compare = std::less<std::tuple<int, int, int> >; _Alloc = std::allocator<std::tuple<int, int, int> >; const_iterator = std::_Rb_tree<std::tuple<int, int, int>, std::tuple<int, int, int>, std::_Identity<std::tuple<int, int, int> >, std::less<std::tuple<int, int, int> >, std::allocator<std::tuple<int, int, int> > >::const_iterator; key_type = std::tuple<int, int, int>]'
  800 |       find(const key_type& __x) const
      |       ^~~~
/usr/include/c++/13/bits/stl_set.h:800:28: note:   no known conversion for argument 1 from 'const std::tuple<int, int, int, int>' to 'const std::set<std::tuple<int, int, int> >::key_type&' {aka 'const std::tuple<int, int, int>&'}
  800 |       find(const key_type& __x) const
      |            ~~~~~~~~~~~~~~~~^~~
bridges.cpp:88:71: error: no matching function for call to 'std::vector<std::tuple<int, int, int> >::push_back(const std::tuple<int, int, int, int>&)'
   88 |         for(auto & x : es) if(mods.find(x) == mods.end()) uc.push_back(x);
      |                                                           ~~~~~~~~~~~~^~~
In file included from /usr/include/c++/13/vector:66,
                 from /usr/include/c++/13/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/13/bits/stdc++.h:53:
/usr/include/c++/13/bits/stl_vector.h:1281:7: note: candidate: 'constexpr void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::tuple<int, int, int>; _Alloc = std::allocator<std::tuple<int, int, int> >; value_type = std::tuple<int, int, int>]'
 1281 |       push_back(const value_type& __x)
      |       ^~~~~~~~~
/usr/include/c++/13/bits/stl_vector.h:1281:35: note:   no known conversion for argument 1 from 'const std::tuple<int, int, int, int>' to 'const std::vector<std::tuple<int, int, int> >::value_type&' {aka 'const std::tuple<int, int, int>&'}
 1281 |       push_back(const value_type& __x)
      |                 ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/13/bits/stl_vector.h:1298:7: note: candidate: 'constexpr void std::vector<_Tp, _Alloc>::push_back(value_type&&) [with _Tp = std::tuple<int, int, int>; _Alloc = std::allocator<std::tuple<int, int, int> >; value_type = std::tuple<int, int, int>]'
 1298 |       push_back(value_type&& __x)
      |       ^~~~~~~~~
/usr/include/c++/13/bits/stl_vector.h:1298:30: note:   no known conversion for argument 1 from 'const std::tuple<int, int, int, int>' to 'std::vector<std::tuple<int, int, int> >::value_type&&' {aka 'std::tuple<int, int, int>&&'}
 1298 |       push_back(value_type&& __x)
      |                 ~~~~~~~~~~~~~^~~