Problem p02763 (C++)

Buggy submission (status: Runtime Error):
#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()                                                              \
  {                                                                            \
    cin.tie(0);                                                                \
    cout.sync_with_stdio(false);                                               \
  }
#define reach(i, a) for (auto i : a)
#define rep(i, n) for (int i = 0; i < ((int)n); i++)
#define REP(i, n) for (int i = 0; i <= ((int)n); i++)
#define srep(i, a, n) for (int i = a; i < ((int)n); i++)
#define SREP(i, a, n) for (int i = a; i <= ((int)n); i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define RREP(i, n) for (int i = n; i >= 0; i--)
#define all(a) (a).begin(), (a).end()
#define mp(a, b) make_pair(a, b)
#define mt make_tuple
#define pb push_back
template <typename T> istream &operator>>(istream &is, vector<T> &vec) {
  for (T &x : vec)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &vec) {
  os << "[";
  rep(i, vec.size()) os << (i ? ", " : "") << vec[i];
  os << "]";
  return os;
}
template <typename T> istream &operator>>(istream &is, pair<T, T> &p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, pair<T, T> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T> bool operator<(vector<T> &a, vector<T> &b) {
  rep(i, a.size()) {
    if (i == b.size())
      return false;
    if (a[i] < b[i])
      return true;
    else if (a[i] > b[i])
      return false;
  }
  return false;
}
template <typename T> bool operator>(vector<T> &a, vector<T> &b) {
  rep(i, a.size()) {
    if (i == b.size())
      return true;
    if (a[i] < b[i])
      return false;
    else if (a[i] > b[i])
      return true;
  }
  return false;
}
int bitcnt(ll x) {
  x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
  x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
  x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
  x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
  x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
  x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
  return x;
}
int bitcnt(int x) {
  x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
  x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
  x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
  x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
  x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
  return x;
}
ll sqrtll(ll x) {
  ll left = 0, right = x;
  rep(i, 100) {
    ll mid = (left + right) >> 1;
    if (mid * mid <= x)
      left = mid;
    else
      right = mid;
  }
  return left;
}
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
#define debug(x) printf("Case #%d: ", x)
#define DEBUG 0
const ld infl = 1e100;
const ll mod = 1e9 + 7;
const ld eps = 1e-9;
const ll inf = 1e15;
const int dx[] = {1, 0, -1, 0, 0};
const int dy[] = {0, 1, 0, -1, 0};

int N;
int bit[500010][26];

void init(int n) {
  N = 1;
  while (n >= N) {
    N <<= 1;
  }
}

void add(int key, int k, int a) {
  k++;
  while (k <= N) {
    bit[k][key] += a;
    k += -k & k;
  }
}

int sum(int key, int k) {
  k++;
  int res = 0;
  while (k > 0) {
    res += bit[k][key];
    k -= -k & k;
  }
  return res;
}

int main() {
  int n;
  cin >> n;
  init(n);
  string s;
  cin >> s;
  rep(i, n) { add(s[i] - 'a', i, 1); }
  int q;
  cin >> q;
  while (q--) {
    int num;
    cin >> num;
    if (num == 1) {
      int idx;
      char to;
      scanf("%d %c", &idx, &to);
      idx--;
      add(s[idx] - 'a', idx, -1);
      add(to - 'a', idx, 1);
      s[idx] = to;
    } else {
      int l, r;
      cin >> l >> r;
      l--;
      r--;
      int res = 0;
      rep(i, 26) {
        if (sum(i, r) - sum(i, l - 1))
          res++;
      }
      cout << res << endl;
    }
  }
  return 0;
}

Fixed submission:
#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()                                                              \
  {                                                                            \
    cin.tie(0);                                                                \
    cout.sync_with_stdio(false);                                               \
  }
#define reach(i, a) for (auto i : a)
#define rep(i, n) for (int i = 0; i < ((int)n); i++)
#define REP(i, n) for (int i = 0; i <= ((int)n); i++)
#define srep(i, a, n) for (int i = a; i < ((int)n); i++)
#define SREP(i, a, n) for (int i = a; i <= ((int)n); i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define RREP(i, n) for (int i = n; i >= 0; i--)
#define all(a) (a).begin(), (a).end()
#define mp(a, b) make_pair(a, b)
#define mt make_tuple
#define pb push_back
template <typename T> istream &operator>>(istream &is, vector<T> &vec) {
  for (T &x : vec)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &vec) {
  os << "[";
  rep(i, vec.size()) os << (i ? ", " : "") << vec[i];
  os << "]";
  return os;
}
template <typename T> istream &operator>>(istream &is, pair<T, T> &p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, pair<T, T> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T> bool operator<(vector<T> &a, vector<T> &b) {
  rep(i, a.size()) {
    if (i == b.size())
      return false;
    if (a[i] < b[i])
      return true;
    else if (a[i] > b[i])
      return false;
  }
  return false;
}
template <typename T> bool operator>(vector<T> &a, vector<T> &b) {
  rep(i, a.size()) {
    if (i == b.size())
      return true;
    if (a[i] < b[i])
      return false;
    else if (a[i] > b[i])
      return true;
  }
  return false;
}
int bitcnt(ll x) {
  x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
  x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
  x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
  x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
  x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
  x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
  return x;
}
int bitcnt(int x) {
  x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
  x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
  x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
  x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
  x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
  return x;
}
ll sqrtll(ll x) {
  ll left = 0, right = x;
  rep(i, 100) {
    ll mid = (left + right) >> 1;
    if (mid * mid <= x)
      left = mid;
    else
      right = mid;
  }
  return left;
}
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
#define debug(x) printf("Case #%d: ", x)
#define DEBUG 0
const ld infl = 1e100;
const ll mod = 1e9 + 7;
const ld eps = 1e-9;
const ll inf = 1e15;
const int dx[] = {1, 0, -1, 0, 0};
const int dy[] = {0, 1, 0, -1, 0};

int N;
int bit[1000010][26];

void init(int n) {
  N = 1;
  while (n >= N) {
    N <<= 1;
  }
}

void add(int key, int k, int a) {
  k++;
  while (k <= N) {
    bit[k][key] += a;
    k += -k & k;
  }
}

int sum(int key, int k) {
  k++;
  int res = 0;
  while (k > 0) {
    res += bit[k][key];
    k -= -k & k;
  }
  return res;
}

int main() {
  int n;
  cin >> n;
  init(n);
  string s;
  cin >> s;
  rep(i, n) { add(s[i] - 'a', i, 1); }
  int q;
  cin >> q;
  while (q--) {
    int num;
    cin >> num;
    if (num == 1) {
      int idx;
      char to;
      scanf("%d %c", &idx, &to);
      idx--;
      add(s[idx] - 'a', idx, -1);
      add(to - 'a', idx, 1);
      s[idx] = to;
    } else {
      int l, r;
      cin >> l >> r;
      l--;
      r--;
      int res = 0;
      rep(i, 26) {
        if (sum(i, r) - sum(i, l - 1))
          res++;
      }
      cout << res << endl;
    }
  }
  return 0;
}