Problem p02763 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

// 定数
const long long MOD1 = 1000000007;
const long long MOD2 = 998244353;
const long double PI = 3.1415926535897932;
const long long MAXLL = 9223372036854775807;
const long long INF = 2305843009213693951;
const long long dx[] = {0, 1, 0, -1, 1, -1, 1, -1};
const long long dy[] = {1, 0, -1, 0, 1, 1, -1, -1};

// 省略
#define ll long long
#define ull unsigned long long
#define ld long double
#define uld unsigned long double
#define pll pair<long long, long long>
#define vl vector<long long>
#define vvl vector<vector<long long>>
#define vvvl vector<vector<vector<long long>>>
#define vc vector<char>
#define vvc vector<vector<char>>
#define vs vector<string>
#define vb vector<bool>
#define vvb vector<vector<bool>>
#define vp vector<pair<long long, long long>>
#define umap unordered_map
#define uset unordered_set
#define Lqueue priority_queue<long long>
#define Squeue priority_queue<long long, vector<long long>, greater<long long>>
#define fi first
#define se second
#define mp make_pair
#define eb emplace_back

// マクロ
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rbf(a, x) for (auto &a : x)
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
#define rep2(i, s, n) for (long long i = (s); i < (long long)(n); i++)
#define bitrep(i, s, n) for (long long i = (s); i < (1LL << (n)); i++)
#define bitcheck(bit, i) (bit) & (1LL << (i))
#define Maxe(x) *max_element((x).begin(), (x).end())
#define Mine(x) *min_element((x).begin(), (x).end())
#define Size(x) ((long long)(x).size())
#define Lin(s) getline(cin, (s))

// Yes,No
void Yes(bool a) { cout << (a ? "Yes" : "No") << endl; }
void YES(bool a) { cout << (a ? "YES" : "NO") << endl; }

// MAX,MIN
template <class T, class U> auto max(T a, U b) { return a > b ? a : b; }
template <class T, class U> auto min(T a, U b) { return a < b ? a : b; }

// 最大公約数,最小公倍数
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }

// 切り上げ除算
long long cutup(long long a, long long b) { return (a + b - 1) / b; }

// 累乗
template <typename t> constexpr t my_pow(t a, long long b) {
  if (b == 0)
    return 1;
  if (a == 0)
    return 0;
  t x = 1;
  while (b > 0) {
    if (b & 1LL)
      x *= a;
    a *= a;
    b >>= 1LL;
  }
  return x;
}
#define pow my_pow

// chmin,chmax
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

// 組み合わせ O(r)
template <typename t> constexpr t nCr(t n, long long r) {
  if (r == 0)
    return 1;
  if (n == 0)
    return 0;
  if (n < r)
    return 0;
  t x = 1;
  for (long long i = 1; i <= r; i++) {
    x *= n - i + 1;
    x /= i;
  }
  return x;
}

// main関数
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, q;
  string s;
  cin >> n >> s >> q;
  vector<set<int>> C(26);
  rep(i, n) C[s[i] - 'a'].insert(i + 1);
  rep(i, q) {
    int a;
    cin >> a;
    if (a == 1) {
      int b;
      char c;
      cin >> b >> c;
      C[s[b - 1] - 'a'].erase(b);
      C[c - 'a'].insert(b);
      s[b - 1] = c;
    } else {
      int l, r;
      cin >> l >> r;
      int res = 0;
      rep(j, 26) {
        if (lower_bound(all(C[j]), l) != upper_bound(all(C[j]), r))
          res++;
      }
      cout << res << "\n";
    }
  }
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;

// 定数
const long long MOD1 = 1000000007;
const long long MOD2 = 998244353;
const long double PI = 3.1415926535897932;
const long long MAXLL = 9223372036854775807;
const long long INF = 2305843009213693951;
const long long dx[] = {0, 1, 0, -1, 1, -1, 1, -1};
const long long dy[] = {1, 0, -1, 0, 1, 1, -1, -1};

// 省略
#define ll long long
#define ull unsigned long long
#define ld long double
#define uld unsigned long double
#define pll pair<long long, long long>
#define vl vector<long long>
#define vvl vector<vector<long long>>
#define vvvl vector<vector<vector<long long>>>
#define vc vector<char>
#define vvc vector<vector<char>>
#define vs vector<string>
#define vb vector<bool>
#define vvb vector<vector<bool>>
#define vp vector<pair<long long, long long>>
#define umap unordered_map
#define uset unordered_set
#define Lqueue priority_queue<long long>
#define Squeue priority_queue<long long, vector<long long>, greater<long long>>
#define fi first
#define se second
#define mp make_pair
#define eb emplace_back

// マクロ
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rbf(a, x) for (auto &a : x)
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
#define rep2(i, s, n) for (long long i = (s); i < (long long)(n); i++)
#define bitrep(i, s, n) for (long long i = (s); i < (1LL << (n)); i++)
#define bitcheck(bit, i) (bit) & (1LL << (i))
#define Maxe(x) *max_element((x).begin(), (x).end())
#define Mine(x) *min_element((x).begin(), (x).end())
#define Size(x) ((long long)(x).size())
#define Lin(s) getline(cin, (s))

// Yes,No
void Yes(bool a) { cout << (a ? "Yes" : "No") << endl; }
void YES(bool a) { cout << (a ? "YES" : "NO") << endl; }

// MAX,MIN
template <class T, class U> auto max(T a, U b) { return a > b ? a : b; }
template <class T, class U> auto min(T a, U b) { return a < b ? a : b; }

// 最大公約数,最小公倍数
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }

// 切り上げ除算
long long cutup(long long a, long long b) { return (a + b - 1) / b; }

// 累乗
template <typename t> constexpr t my_pow(t a, long long b) {
  if (b == 0)
    return 1;
  if (a == 0)
    return 0;
  t x = 1;
  while (b > 0) {
    if (b & 1LL)
      x *= a;
    a *= a;
    b >>= 1LL;
  }
  return x;
}
#define pow my_pow

// chmin,chmax
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

// 組み合わせ O(r)
template <typename t> constexpr t nCr(t n, long long r) {
  if (r == 0)
    return 1;
  if (n == 0)
    return 0;
  if (n < r)
    return 0;
  t x = 1;
  for (long long i = 1; i <= r; i++) {
    x *= n - i + 1;
    x /= i;
  }
  return x;
}

// main関数
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, q;
  string s;
  cin >> n >> s >> q;
  vector<set<int>> C(26);
  rep(i, n) C[s[i] - 'a'].insert(i + 1);
  rep(i, q) {
    int a;
    cin >> a;
    if (a == 1) {
      int b;
      char c;
      cin >> b >> c;
      C[s[b - 1] - 'a'].erase(b);
      C[c - 'a'].insert(b);
      s[b - 1] = c;
    } else {
      int l, r;
      cin >> l >> r;
      int res = 0;
      rep(j, 26) {
        if (C[j].lower_bound(l) != C[j].upper_bound(r))
          res++;
      }
      cout << res << "\n";
    }
  }
}