Problem p02763 (C++)

Buggy submission (status: Time Limit Exceeded):
#include "bits/stdc++.h"

using namespace std;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef vector<VVLL> VVVLL;
typedef pair<LL, LL> PLL;
typedef vector<PLL> VPLL;

#define SORT_ASC(c) sort((c).begin(), (c).end())
#define SORT_DESC(c)                                                           \
  sort((c).begin(), (c).end(), greater<typeof((c).begin())>())

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define FORL(i, a, b) for (LL i = (a); i < (b); ++i)
#define REPL(i, n) FORL(i, 0, n)
#define SIZE(a) int((a).size())
#define ALL(a) (a).begin(), (a).end()

const double EPS = 1e-10;
const double PI = acos(-1.0);

// debug func
template <typename T> void vprint(vector<T> v) {
  for (auto x : v) {
    cerr << x << " ";
  }
  cerr << endl;
}

template <typename T> void vvprint(vector<vector<T>> vv) {
  REP(i, SIZE(vv)) {
    REP(j, SIZE(vv[i])) { cerr << vv[i][j] << " "; }
    cerr << endl;
  }
}

template <typename T1, typename T2> void vpprint(vector<pair<T1, T2>> vp) {
  REP(i, SIZE(vp)) { cerr << vp[i].first << ", " << vp[i].second << endl; }
}

template <typename T1, typename T2> void mprint(map<T1, T2> m) {
  for (auto x : m)
    cerr << x.first << ", " << x.second << endl;
}

template <typename Iterator>
inline bool next_combination(const Iterator first, Iterator k,
                             const Iterator last) {
  /* Credits: Thomas Draper */
  if ((first == last) || (first == k) || (last == k))
    return false;
  Iterator itr1 = first;
  Iterator itr2 = last;
  ++itr1;
  if (last == itr1)
    return false;
  itr1 = last;
  --itr1;
  itr1 = k;
  --itr2;
  while (first != itr1) {
    if (*--itr1 < *itr2) {
      Iterator j = k;
      while (!(*itr1 < *j))
        ++j;
      iter_swap(itr1, j);
      ++itr1;
      ++j;
      itr2 = k;
      rotate(itr1, j, last);
      while (last != j) {
        ++j;
        ++itr2;
      }
      rotate(k, itr2, last);
      return true;
    }
  }
  rotate(first, k, last);
  return false;
}

inline double get_time_sec(void) {
  return static_cast<double>(chrono::duration_cast<chrono::nanoseconds>(
                                 chrono::steady_clock::now().time_since_epoch())
                                 .count()) /
         1000000000;
}

template <typename T> T gcd(T a, T b) {
  if (a > b)
    swap(a, b);
  if (a == 0)
    return b;
  else
    return gcd(b % a, a);
}

template <typename T> T lcm(T a, T b) { return (a / gcd(a, b)) * b; }

template <typename T> map<T, T> prime_list(T n) {
  map<T, T> ret;
  for (T i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      ret[i] = 0;
      while (n % i == 0) {
        n /= i;
        ret[i]++;
      }
    }
  }
  if (n != 1)
    ret[n]++;
  return ret;
}

#define MOD 1000000007

LL mypow(LL a, LL n) {
  if (n == 0)
    return 1;
  if (n == 1)
    return a % MOD;
  if (n % 2 == 1)
    return (a * mypow(a, n - 1)) % MOD;
  LL t = mypow(a, n / 2);
  return (t * t) % MOD;
}

#define FACT_SZ 100010
VLL _fact, _inv;
bool _fact_flg = true;

void _fact_init() {
  _fact = VLL(FACT_SZ);
  _inv = VLL(FACT_SZ);
  _fact[0] = 1;
  FOR(i, 1, FACT_SZ) _fact[i] = (_fact[i - 1] * i) % MOD;
  _inv[FACT_SZ - 1] = mypow(_fact[FACT_SZ - 1], MOD - 2);
  for (int i = FACT_SZ - 2; i >= 0; i--) {
    _inv[i] = ((i + 1) * _inv[i + 1]) % MOD;
  }
}

LL mycomb(LL n, LL k) {
  if (_fact_flg) {
    _fact_flg = false;
    _fact_init();
  }
  if (n < k)
    return 0;
  return (((_fact[n] * _inv[k]) % MOD) * _inv[n - k]) % MOD;
}

VLL par, rnk, sz;

int root(int x) {
  if (par[x] == x)
    return x;
  else
    return par[x] = root(par[x]);
}

bool same(int x, int y) {
  x = root(x);
  y = root(y);
  return x == y;
}

void unite(int x, int y) {
  x = root(x);
  y = root(y);
  if (rnk[x] < rnk[y]) {
    par[x] = y;
    // sz[y] += sz[x];
  } else {
    par[y] = x;
    // sz[x] += sz[y];
    if (rnk[x] == rnk[y])
      rnk[x]++;
  }
}

#define INF 1e15

int main(void) {
  LL n;
  string s;
  cin >> n >> s;
  vector<set<int>> vs(26);
  REP(i, n) { vs[s[i] - 'a'].insert(i); }
  int q;
  cin >> q;
  REP(hoge, q) {
    int type;
    cin >> type;
    if (type == 1) {
      int i;
      char c;
      cin >> i >> c;
      i--;
      REP(j, 26) {
        if (vs[j].count(i)) {
          vs[j].erase(i);
          break;
        }
      }
      vs[c - 'a'].insert(i);
    } else {
      int l, r;
      cin >> l >> r;
      l--, r--;
      int cnt = 0;
      REP(i, 26) {
        auto it = lower_bound(ALL(vs[i]), l);
        if (it == vs[i].end())
          continue;
        if (*it <= r)
          cnt++;
      }
      cout << cnt << endl;
    }
  }
}

Fixed submission:
#include "bits/stdc++.h"

using namespace std;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef vector<VVLL> VVVLL;
typedef pair<LL, LL> PLL;
typedef vector<PLL> VPLL;

#define SORT_ASC(c) sort((c).begin(), (c).end())
#define SORT_DESC(c)                                                           \
  sort((c).begin(), (c).end(), greater<typeof((c).begin())>())

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define FORL(i, a, b) for (LL i = (a); i < (b); ++i)
#define REPL(i, n) FORL(i, 0, n)
#define SIZE(a) int((a).size())
#define ALL(a) (a).begin(), (a).end()

const double EPS = 1e-10;
const double PI = acos(-1.0);

// debug func
template <typename T> void vprint(vector<T> v) {
  for (auto x : v) {
    cerr << x << " ";
  }
  cerr << endl;
}

template <typename T> void vvprint(vector<vector<T>> vv) {
  REP(i, SIZE(vv)) {
    REP(j, SIZE(vv[i])) { cerr << vv[i][j] << " "; }
    cerr << endl;
  }
}

template <typename T1, typename T2> void vpprint(vector<pair<T1, T2>> vp) {
  REP(i, SIZE(vp)) { cerr << vp[i].first << ", " << vp[i].second << endl; }
}

template <typename T1, typename T2> void mprint(map<T1, T2> m) {
  for (auto x : m)
    cerr << x.first << ", " << x.second << endl;
}

template <typename Iterator>
inline bool next_combination(const Iterator first, Iterator k,
                             const Iterator last) {
  /* Credits: Thomas Draper */
  if ((first == last) || (first == k) || (last == k))
    return false;
  Iterator itr1 = first;
  Iterator itr2 = last;
  ++itr1;
  if (last == itr1)
    return false;
  itr1 = last;
  --itr1;
  itr1 = k;
  --itr2;
  while (first != itr1) {
    if (*--itr1 < *itr2) {
      Iterator j = k;
      while (!(*itr1 < *j))
        ++j;
      iter_swap(itr1, j);
      ++itr1;
      ++j;
      itr2 = k;
      rotate(itr1, j, last);
      while (last != j) {
        ++j;
        ++itr2;
      }
      rotate(k, itr2, last);
      return true;
    }
  }
  rotate(first, k, last);
  return false;
}

inline double get_time_sec(void) {
  return static_cast<double>(chrono::duration_cast<chrono::nanoseconds>(
                                 chrono::steady_clock::now().time_since_epoch())
                                 .count()) /
         1000000000;
}

template <typename T> T gcd(T a, T b) {
  if (a > b)
    swap(a, b);
  if (a == 0)
    return b;
  else
    return gcd(b % a, a);
}

template <typename T> T lcm(T a, T b) { return (a / gcd(a, b)) * b; }

template <typename T> map<T, T> prime_list(T n) {
  map<T, T> ret;
  for (T i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      ret[i] = 0;
      while (n % i == 0) {
        n /= i;
        ret[i]++;
      }
    }
  }
  if (n != 1)
    ret[n]++;
  return ret;
}

#define MOD 1000000007

LL mypow(LL a, LL n) {
  if (n == 0)
    return 1;
  if (n == 1)
    return a % MOD;
  if (n % 2 == 1)
    return (a * mypow(a, n - 1)) % MOD;
  LL t = mypow(a, n / 2);
  return (t * t) % MOD;
}

#define FACT_SZ 100010
VLL _fact, _inv;
bool _fact_flg = true;

void _fact_init() {
  _fact = VLL(FACT_SZ);
  _inv = VLL(FACT_SZ);
  _fact[0] = 1;
  FOR(i, 1, FACT_SZ) _fact[i] = (_fact[i - 1] * i) % MOD;
  _inv[FACT_SZ - 1] = mypow(_fact[FACT_SZ - 1], MOD - 2);
  for (int i = FACT_SZ - 2; i >= 0; i--) {
    _inv[i] = ((i + 1) * _inv[i + 1]) % MOD;
  }
}

LL mycomb(LL n, LL k) {
  if (_fact_flg) {
    _fact_flg = false;
    _fact_init();
  }
  if (n < k)
    return 0;
  return (((_fact[n] * _inv[k]) % MOD) * _inv[n - k]) % MOD;
}

VLL par, rnk, sz;

int root(int x) {
  if (par[x] == x)
    return x;
  else
    return par[x] = root(par[x]);
}

bool same(int x, int y) {
  x = root(x);
  y = root(y);
  return x == y;
}

void unite(int x, int y) {
  x = root(x);
  y = root(y);
  if (rnk[x] < rnk[y]) {
    par[x] = y;
    // sz[y] += sz[x];
  } else {
    par[y] = x;
    // sz[x] += sz[y];
    if (rnk[x] == rnk[y])
      rnk[x]++;
  }
}

#define INF 1e15

int main(void) {
  LL n;
  string s;
  cin >> n >> s;
  vector<set<int>> vs(26);
  REP(i, n) { vs[s[i] - 'a'].insert(i); }
  int q;
  cin >> q;
  REP(hoge, q) {
    int type;
    cin >> type;
    if (type == 1) {
      int i;
      char c;
      cin >> i >> c;
      i--;
      REP(j, 26) {
        if (vs[j].count(i)) {
          vs[j].erase(i);
          break;
        }
      }
      vs[c - 'a'].insert(i);
    } else {
      int l, r;
      cin >> l >> r;
      l--, r--;
      int cnt = 0;
      REP(i, 26) {
        auto it = vs[i].lower_bound(l);
        if (it == vs[i].end())
          continue;
        if (*it <= r)
          cnt++;
      }
      cout << cnt << endl;
    }
  }
}