Language: C++

#include <bits/stdc++.h>
#include <math.h>

using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
typedef long long ll;
using Graph = vector<vector<int>>;
typedef long long ll;
typedef pair<int, int> P;

const int MOD = 1000000007;
const int INF_32 = 1LL << 30;
const int64_t INF_64 = 1LL << 60;

/*
18 26
*/
int main()
{
    int n;
    cin >> n;
    string s;
    cin >> s;
    int q;
    cin >> q;

    vector<set<int>> a(26);
    for (int i = 0; i < n; i++) {
        char c = s[i];
        a[(int)(c - 'a')].insert(i);
    }

    for (int i = 0; i < q; i++) {
        int type;
        cin >> type;
        if (type == 1) {
            int index;
            char new_c;
            cin >> index >> new_c;
            index--;
            char old_c = s[index];
            s[index] = new_c;
            a[(int)(old_c - 'a')].erase(index);
            a[(int)(new_c - 'a')].insert(index);
        } else {
            int l, r;
            cin >> l >> r;
            l--, r--;
            int cnt = 0;
            for (int j = 0; j < 26; j++) {
                set<int> bst = a[j];
                auto lower_it = lower_bound(bst.begin(), bst.end(), l);
                if (lower_it - bst.begin() < r)
                    cnt++;
                // auto upper_it = upper_bound(bst.begin(), bst.end(), r);
                // if (lower_it != upper_it)
                //     cnt++;
            }
            cout << cnt << endl;
        }
    }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:54:30: error: no match for 'operator-' (operand types are 'std::_Rb_tree_const_iterator<int>' and 'std::set<int>::iterator' {aka 'std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator'})
   54 |                 if (lower_it - bst.begin() < r)
      |                     ~~~~~~~~ ^ ~~~~~~~~~~~
      |                     |                   |
      |                     |                   _Rb_tree_const_iterator<[...]>
      |                     _Rb_tree_const_iterator<[...]>
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::move_iterator<_IteratorL>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:370:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::complex<_Tp>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/complex:379:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const _Tp&)'
  379 |     operator-(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:379:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::complex<_Tp>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/complex:388:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const _Tp&, const complex<_Tp>&)'
  388 |     operator-(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:388:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::set<int>::iterator' {aka 'std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator'} is not derived from 'const std::complex<_Tp>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/complex:465:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&)'
  465 |     operator-(const complex<_Tp>& __x)
      |     ^~~~~~~~
/usr/include/c++/14/complex:465:5: note:   candidate expects 1 argument, 2 provided
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::set<int>::iterator' {aka 'std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::set<int>::iterator' {aka 'std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const valarray<_Tp>&, const valarray<_Tp>&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::valarray<_Tp>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:54:42: note:   'std::_Rb_tree_const_iterator<int>' is not derived from 'const std::valarray<_Tp>'
   54 |                 if (lower_it - bst.begin() < r)
      |                                          ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::op