Problem p02763 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
const long long INF = 1LL << 60;
const long long MOD = 1000000007;
const double PI = acos(-1.0);
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = (n - 1); i >= 0; --i)
#define perm(c)                                                                \
  sort(ALL(c));                                                                \
  for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define to_s to_string
#define len(v) (ll) v.size()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define print(x) cout << (x) << '\n'
#define drop(x) cout << (x) << '\n', exit(0)
#define debug(x) cout << #x << ": " << (x) << '\n'
using namespace std;
using ll = long long;
typedef pair<ll, ll> P;
typedef vector<ll> vec;
typedef vector<vector<ll>> vec2;
typedef vector<vector<vector<ll>>> vec3;
template <class S, class T> inline bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class S, class T> inline bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
inline ll msb(ll v) { return 1 << (31 - __builtin_clzll(v)); }
inline ll devc(ll x, ll y) { return (x + y - 1) / y; }

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3> &t) {
  os << get<0>(t) << " " << get<1>(t) << " " << get<2>(t);
  return os;
}

template <typename T1, typename T2, typename T3>
istream &operator>>(istream &is, tuple<T1, T2, T3> &t) {
  is >> get<0>(t) >> get<1>(t) >> get<2>(t);
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); ++i) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

/*---------------------------------    Tools
 * ------------------------------------------*/
template <typename T> vector<T> cumsum(const vector<T> &X) {
  vector<T> res(X.size() + 1, 0);
  for (int i = 0; i < X.size(); ++i)
    res[i + 1] += res[i] + X[i];
  return res;
}

template <typename S, typename T, typename F>
pair<T, T> bisearch(S left, T right, F f) {
  while (abs(right - left) > 1) {
    T mid = (right + left) / 2;
    if (f(mid))
      right = mid;
    else
      left = mid;
  }
  return {left, right};
}

template <typename S, typename T, typename F>
double trisearch(S left, T right, F f, int maxLoop = 90) {
  double low = left, high = right;
  while (maxLoop--) {
    double mid_left = high / 3 + low * 2 / 3;
    double mid_right = high * 2 / 3 + low / 3;
    if (f(mid_left) >= f(mid_right))
      low = mid_left;
    else
      high = mid_right;
  }
  return (low + high) * 0.5;
}

// Def of Monoid
// Suppose that S is a set and ● is some binary opeartion S x S -> S
// then S with ● is a monoid if it satisfies the following two:
//  Associativity(結合則)
//   For all a,b and c in S, the equation (a ● b) ● c = a ● (b ● c) holds
//  Identitiy element(単位元の存在)
//   There exisits an element e in S such that for every element a in S,
//   the equations e ● a = a ● e = a holds

// Eample of Monoid
//+, *, and, or, xor, min, max

// Build O(N)
// Query O(log N)
//- query(a,b) : applay operation to the range [a, b)
//- update(k,x) : change k-th element to x
//- operator[k] : return k-th element

template <typename Monoid> class SegmentTree {
private:
  using F = function<Monoid(Monoid, Monoid)>;

  long long sz;
  vector<Monoid> seg;
  const F f;
  const Monoid e;

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

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

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

  void update(long long 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(long long a, long long b) {
    Monoid L = e, R = e;
    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]; }
};

/*------------------------------- Main Code Here
 * -----------------------------------------*/

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

  vector<SegmentTree<ll>> trees(
      26, SegmentTree<ll>(
              N + 1, [&](ll x, ll y) { return x or y; }, 0));
  string S;
  cin >> S;

  rep(i, len(S)) trees[S[i] - 'a'].set(i, 1);
  rep(i, len(S)) trees[i].build();

  ll Q;
  cin >> Q;
  rep(_, Q) {
    ll q;
    cin >> q;
    if (q == 1) {
      ll i;
      char c;
      cin >> i >> c;
      --i;
      trees[S[i] - 'a'].update(i, 0);
      trees[c - 'a'].update(i, 1);
      S[i] = c;
    }
    if (q == 2) {
      ll l, r;
      cin >> l >> r;
      --l;
      ll ans = 0;
      rep(i, 26) ans += trees[i].query(l, r);
      print(ans);
    }
  }

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
const long long INF = 1LL << 60;
const long long MOD = 1000000007;
const double PI = acos(-1.0);
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = (n - 1); i >= 0; --i)
#define perm(c)                                                                \
  sort(ALL(c));                                                                \
  for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define to_s to_string
#define len(v) (ll) v.size()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define print(x) cout << (x) << '\n'
#define drop(x) cout << (x) << '\n', exit(0)
#define debug(x) cout << #x << ": " << (x) << '\n'
using namespace std;
using ll = long long;
typedef pair<ll, ll> P;
typedef vector<ll> vec;
typedef vector<vector<ll>> vec2;
typedef vector<vector<vector<ll>>> vec3;
template <class S, class T> inline bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class S, class T> inline bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
inline ll msb(ll v) { return 1 << (31 - __builtin_clzll(v)); }
inline ll devc(ll x, ll y) { return (x + y - 1) / y; }

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3> &t) {
  os << get<0>(t) << " " << get<1>(t) << " " << get<2>(t);
  return os;
}

template <typename T1, typename T2, typename T3>
istream &operator>>(istream &is, tuple<T1, T2, T3> &t) {
  is >> get<0>(t) >> get<1>(t) >> get<2>(t);
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); ++i) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

/*---------------------------------    Tools
 * ------------------------------------------*/
template <typename T> vector<T> cumsum(const vector<T> &X) {
  vector<T> res(X.size() + 1, 0);
  for (int i = 0; i < X.size(); ++i)
    res[i + 1] += res[i] + X[i];
  return res;
}

template <typename S, typename T, typename F>
pair<T, T> bisearch(S left, T right, F f) {
  while (abs(right - left) > 1) {
    T mid = (right + left) / 2;
    if (f(mid))
      right = mid;
    else
      left = mid;
  }
  return {left, right};
}

template <typename S, typename T, typename F>
double trisearch(S left, T right, F f, int maxLoop = 90) {
  double low = left, high = right;
  while (maxLoop--) {
    double mid_left = high / 3 + low * 2 / 3;
    double mid_right = high * 2 / 3 + low / 3;
    if (f(mid_left) >= f(mid_right))
      low = mid_left;
    else
      high = mid_right;
  }
  return (low + high) * 0.5;
}

// Def of Monoid
// Suppose that S is a set and ● is some binary opeartion S x S -> S
// then S with ● is a monoid if it satisfies the following two:
//  Associativity(結合則)
//   For all a,b and c in S, the equation (a ● b) ● c = a ● (b ● c) holds
//  Identitiy element(単位元の存在)
//   There exisits an element e in S such that for every element a in S,
//   the equations e ● a = a ● e = a holds

// Eample of Monoid
//+, *, and, or, xor, min, max

// Build O(N)
// Query O(log N)
//- query(a,b) : applay operation to the range [a, b)
//- update(k,x) : change k-th element to x
//- operator[k] : return k-th element

template <typename Monoid> class SegmentTree {
private:
  using F = function<Monoid(Monoid, Monoid)>;

  long long sz;
  vector<Monoid> seg;
  const F f;
  const Monoid e;

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

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

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

  void update(long long 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(long long a, long long b) {
    Monoid L = e, R = e;
    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]; }
};

/*------------------------------- Main Code Here
 * -----------------------------------------*/

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

  vector<SegmentTree<ll>> trees(
      26, SegmentTree<ll>(
              N + 1, [&](ll x, ll y) { return x or y; }, 0));
  string S;
  cin >> S;

  rep(i, len(S)) trees[S[i] - 'a'].set(i, 1);
  rep(i, 26) trees[i].build();

  ll Q;
  cin >> Q;
  rep(_, Q) {
    ll q;
    cin >> q;
    if (q == 1) {
      ll i;
      char c;
      cin >> i >> c;
      --i;
      trees[S[i] - 'a'].update(i, 0);
      trees[c - 'a'].update(i, 1);
      S[i] = c;
    }
    if (q == 2) {
      ll l, r;
      cin >> l >> r;
      --l;
      ll ans = 0;
      rep(i, 26) ans += trees[i].query(l, r);
      print(ans);
    }
  }

  return 0;
}