Language: C++

#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<long>;
using vs = vector<string>;
using vvi = vector<vector<int>>;
using vvb = vector<vector<bool>>;
using vvc = vector<vector<char>>;
using pii = pair<int, int>;
using pll = pair<long, long>;
#define fix20 cout << fixed << setprecision(20);
#define rep(i,n) for(int i=0; i<(int)(n);i++)
#define MOD 1000000007

int main(){
  long n;
  cin >> n;
  vector<long> a(n);
  vector<vector<long>> data(n);
  long maxi = 0;
  rep(i,n){
    cin >> a.at(i);
    maxi = max(a.at(i),maxi);
    data.at(a.at(i)).push_back(i);
  }
  long ans = 6;
  if(data.at(0).size() == 1){
    cout << 3 << endl;
    return 0;
  }
  rep(i,maxi){
    if(data.at(i).size() < data.at(i+1).size()){
      cout << 0 << endl;
      return 0;
    }
    if(data.at(i) == 0 || data.at(i+1) == 0){
      cout << 0 << endl;
      return 0;
    }
  }
  //cout << maxi << endl;
  for(long i=1;i<=maxi;i++){
    long color = data.at(i-1).size();
    long minus = 0;
    long m = data.at(i).size();
    for(long x : data.at(i)){
      long id = data.at(i-1).size();
      rep(j,data.at(i-1).size()){
        if(x < data.at(i-1).at(j)){
          //if(i == 6) cout << "j is " << j << endl;
          id = j;
          break;
        }
      }
      /*if(i >= 9 ){
        cout << "i:" << i << endl;
        cout << "x:" << x << endl;
        cout << "id:" << id << endl;
        cout << "color:" << color << endl;
      }*/
      long mul = id-minus;
      ans *= mul;
      ans %= MOD;
      color--;
      minus++;
      //if(i==9) cout << "p" << ans << endl;
    }
  }
  cout << ans << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:37:19: error: no match for 'operator==' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} and 'int')
   37 |     if(data.at(i) == 0 || data.at(i+1) == 0){
      |        ~~~~~~~~~~ ^~ ~
      |               |      |
      |               |      int
      |               __gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type {aka std::vector<long int>}
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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::pair<_T1, _T2>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::move_iterator<_IteratorL>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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:37:22: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::vector<long int> >, std::vector<long int> >::value_type' {aka 'std::vector<long int>'} is not derived from 'const std::move_iterator<_IteratorL>'
   37 |     if(data.at(i) == 0 || data.at(i+1) == 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