Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)
#define rep2(i, a, n) for(ll i = a; i < (ll)(n); i++)
#define memi cout << endl
#define kono(n) cout << fixed << setprecision(n)
#define all(c) (c).begin(), (c).end()
#define pb push_back
#define hina cout << ' '
#define in(n) cin >> n
#define in2(n, m) cin >> n >> m
#define in3(n, m, l) cin >> n >> m >> l
#define out(n) cout << n
const ll mei = (ll)1e9 + 7;

int main(){
  ll n, m, a, s, t;
  in2(n, m);
  a = 0;
  vector<ll> c(n - 1);
  rep(i, n)
    c[i] = i + 1;
  vector<vector<ll>> d(n, vector<ll> (0));
  bool h;
  rep(i, m){
    in2(s, t);
    d[s - 1].pb(t - 1);
    d[t - 1].pb(s - 1);
  }
  do{
    h = true;
    rep(i, d[0].size()){
      if(c[0] == d[0][i])
        break;
      if(i == d[0].size() - 1)
        h = false;
    }
    rep(i, n - 2){
      s = c[i];
      if(d[s] == 0)
        h = false;
      else{
      rep(j, d[s].size()){
        if(c[i + 1] == d[s][j])
          break;
        if(j == d[s].size() - 1)
          h = false;
      }
      }
    }
    if(h)
      a++;
  }while(next_permutation(all(c)));
  out(a);
  memi;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:41:15: error: no match for 'operator==' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} and 'int')
   41 |       if(d[s] == 0)
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   41 |       if(d[s] == 0)
      |                  ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::pair<_T1, _T2>'
   41 |       if(d[s] == 0)
      |                  ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::move_iterator<_IteratorL>'
   41 |       if(d[s] == 0)
      |                  ^
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::move_iterator<_IteratorL>'
   41 |       if(d[s] == 0)
      |                  ^
In file included from /usr/include/c++/14/bits/char_traits.h:42,
                 from /usr/include/c++/14/string:42,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
a.cc:41:18: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long long int> >, std::vector<long long int> >::value_type' {aka 'std::vector<long long int>'} is not derived from 'const std::fpos<_StateT>'
   41 |       if(d[s] == 0)
      |                  ^
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 't