Language: C++

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using Vi = vector<int>;
using Vl = vector<ll>;
using Pii = pair<int, int>;
using Pll = pair<ll, ll>;

constexpr int I_INF = numeric_limits<int>::max();
constexpr ll L_INF = numeric_limits<ll>::max();

//==================================


template <typename Monoid>
struct SegmentTree {
    using F = function<Monoid(Monoid, Monoid)>;

    int sz;
    vector<Monoid> seg;

    const F f;
    const Monoid M1;

    SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
        sz = 1;
        while (sz < n) sz <<= 1;
        seg.assign(2 * sz, M1);
    }

    void set(int k, const Monoid &x) {
        seg[k + sz] = x;
    }

    void build() {
        for (int k = sz - 1; k > 0; k--) {
            seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
        }
    }

    void update(int k, const Monoid &x) {
        k += sz;
        seg[k] = x;
        while (k >>= 1) {
            seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
        }
    }

    Monoid query(int a, int b) {
        Monoid L = M1, R = M1;
        for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
            if (a & 1) L = f(L, seg[a++]);
            if (b & 1) R = f(seg[--b], R);
        }
        return f(L, R);
    }

    Monoid operator[](const int &k) const {
        return seg[k + sz];
    }

    template <typename C>
    int find_subtree(int a, const C &check, Monoid &M, bool type) {
        while (a < sz) {
            Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
            if (check(nxt))
                a = 2 * a + type;
            else
                M = nxt, a = 2 * a + 1 - type;
        }
        return a - sz;
    }


    template <typename C>
    int find_first(int a, const C &check) {
        Monoid L = M1;
        if (a <= 0) {
            if (check(f(L, seg[1]))) return find_subtree(1, check, L, false);
            return -1;
        }
        int b = sz;
        for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
            if (a & 1) {
                Monoid nxt = f(L, seg[a]);
                if (check(nxt)) return find_subtree(a, check, L, false);
                L = nxt;
                ++a;
            }
        }
        return -1;
    }

    template <typename C>
    int find_last(int b, const C &check) {
        Monoid R = M1;
        if (b >= sz) {
            if (check(f(seg[1], R))) return find_subtree(1, check, R, true);
            return -1;
        }
        int a = sz;
        for (b += sz; a < b; a >>= 1, b >>= 1) {
            if (b & 1) {
                Monoid nxt = f(seg[--b], R);
                if (check(nxt)) return find_subtree(b, check, R, true);
                R = nxt;
            }
        }
        return -1;
    }
};

using bita = bitset<26>;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll N;
    cin >> N;
    string S;
    cin >> S;

    SegmentTree<bita> seg(N, [](bita a, bita b) { return a | b; }, bita());

    for (int i = 0; i < N; i++) {
        int d = S[i] - 'a';
        bita u;
        u[d] = true;
        seg.set(i, u);
    }

    seg.build();

    ll Q;
    cin >> Q;
    for (int q = 0; q < Q; q++) {
        ll a;
        cin >> a;
        if (a == 1) {
            ll b;
            char c;
            cin >> b >> c;
            bita u;
            u.set(c - 'a');
            seg.update(--b, u);
        }
        else {
            ll b, c;
            cin >> b >> c;
            cout << seg.query(--b, c).count << "\n";
        }
    }



    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:153:18: error: invalid use of non-static member function 'std::size_t std::bitset<_Nb>::count() const [with long unsigned int _Nb = 26; std::size_t = long unsigned int]'
  153 |             cout << seg.query(--b, c).count << "\n";
      |             ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bitset:1366:7: note: declared here
 1366 |       count() const _GLIBCXX_NOEXCEPT
      |       ^~~~~