Language: C++

#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <string>
using namespace std;

long long mypower(long long x, int y){
  long long result = 1;
  while(y > 0){
    result *= x;
    y--;
  }
  return result;
}

long long ishi(long long* C, long long N, long long start, long long* D, vector<vector<long long>> v, vector<vector<long long>> u){
  long long result;
  if(start >= N-2){
    result = 1;
  }else{
    if(D[start] != -1){
      return D[start];
    }

    long long tmpC = C[start];
    long long ite;

    if(tmpC == C[start+1]){
      result = ishi(C, N, start+1, D, v,  u);
    }else{


      if(u[C[start]-1] < v[C[start]-1].size()){
        result = (ishi(C, N, start+1, D, v, 0, u) + ishi(C, N, v[C[start]-1][u[C[start]-1]+1], D, v,  u)) % (mypower(10,9) + 7);
      }else{
        result = ishi(C, N, start+1, D, v,  u);
      }

    }


  }

  //cout << "from " << start << ":" << result << "\n";
  D[start] = result;
  return result;
}


int main(){
  long long N;
  cin >> N;

  long long C[N], D[N];
  vector<vector<long long>> v(N);
  vector<vector<long long>> u(N);
  for(int i=0;i<N;i++){
    cin >> C[i];
    v[C[i]-1].push_back(i);
    u[C[i]-1].push_back(v[C[i]-1].size());
    D[i] = -1;
  }

  //long long vite = 0;
  long long result = ishi(C, N, 0, D, v, u);

  cout << result << "\n";
  return 0;
}


Compiler output:
a.cc: In function 'long long int ishi(long long int*, long long int, long long int, long long int*, std::vector<std::vector<long long int> >, std::vector<std::vector<long long int> >)':
a.cc:36:24: 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 'std::vector<long long int>::size_type' {aka 'long unsigned int'})
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
In file included from /usr/include/c++/14/string:48,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:36:45: note:   'std::vector<long long int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  680 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:680:5: note:   template argument deduction/substitution failed:
a.cc:36:45: note:   'std::vector<long long int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/string_view:688:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  688 |     operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:688:5: note:   template argument deduction/substitution failed:
a.cc:36:45: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long unsigned int'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/bits/basic_string.h:3874:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3874 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3874:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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::basic_string<_CharT, _Traits, _Allocator>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/bits/basic_string.h:3888:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3888 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3888:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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::basic_string<_CharT, _Traits, _Allocator>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
/usr/include/c++/14/bits/basic_string.h:3901:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3901 |     operator<(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3901:5: note:   template argument deduction/substitution failed:
a.cc:36:45: note:   mismatched types 'const _CharT*' and 'std::vector<long long int>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2600:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator<(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2600 |     operator<(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2600:5: note:   template argument deduction/substitution failed:
a.cc:36:45: 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::tuple<_UTypes ...>'
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){
      |                                             ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:5:
/usr/include/c++/14/bits/stl_vector.h:2089:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
 2089 |     operator<(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:2089:5: note:   template argument deduction/substitution failed:
a.cc:36:45: note:   mismatched types 'const std::vector<_Tp, _Alloc>' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'}
   36 |       if(u[C[start]-1] < v[C[start]-1].size()){