Problem p02947 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define REP(i, a, n) for (long long i = (a); i < (long long)(n); ++i)
#define REPC(i, a, n) for (long long i = (a); i <= (long long)(n); ++i)
#define ALL(t) t.begin(), t.end()
#define RALL(t) t.rbegin(), t.rend()
#define MATINIT(type, row, col, init)                                          \
  vector<vector<type>>(row, vector<type>(col, init));
#define Yes(cond) cout << (cond ? "Yes" : "No") << endl;
#define YES(cond) cout << (cond ? "YES" : "NO") << endl;
using namespace std;
using LL = long long;
using ULL = unsigned long long;
template <class T> using VEC = std::vector<T>;
template <class T> using MAT = std::vector<std::vector<T>>;
void DUMP() { cerr << endl; }
template <class Head, class... Tail> void DUMP(Head &&head, Tail &&...tail) {
  cerr << head << ", ";
  DUMP(std::move(tail)...);
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &vec) {
  os << "{";
  for (auto v : vec)
    os << v << ",";
  os << "}";
  return os;
}
template <typename T> ostream &operator<<(ostream &os, set<T> &s) {
  os << "{";
  for (auto p : s)
    os << p << ",";
  os << "}";
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, map<T1, T2> &m) {
  os << "{";
  for (auto p : m)
    os << p << ",";
  os << "}";
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  os << "[" << p.first << " " << p.second << "]";
  return os;
}

int main() {
  int N;
  cin >> N;
  VEC<string> S(N);
  REP(i, 0, N) {
    cin >> S[i];
    sort(ALL(S[i]));
  }
  sort(ALL(S));
  // DUMP(S);
  LL cnt = 0;
  REP(l, 0, N) {
    int r = l + 1;
    while (S[l] == S[r]) {
      r++;
    }
    LL k = r - l;
    cnt += k * (k - 1) / 2;
    l = r - 1;
  }
  cout << cnt << endl;

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#define REP(i, a, n) for (long long i = (a); i < (long long)(n); ++i)
#define REPC(i, a, n) for (long long i = (a); i <= (long long)(n); ++i)
#define ALL(t) t.begin(), t.end()
#define RALL(t) t.rbegin(), t.rend()
#define MATINIT(type, row, col, init)                                          \
  vector<vector<type>>(row, vector<type>(col, init));
#define Yes(cond) cout << (cond ? "Yes" : "No") << endl;
#define YES(cond) cout << (cond ? "YES" : "NO") << endl;
using namespace std;
using LL = long long;
using ULL = unsigned long long;
template <class T> using VEC = std::vector<T>;
template <class T> using MAT = std::vector<std::vector<T>>;
void DUMP() { cerr << endl; }
template <class Head, class... Tail> void DUMP(Head &&head, Tail &&...tail) {
  cerr << head << ", ";
  DUMP(std::move(tail)...);
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &vec) {
  os << "{";
  for (auto v : vec)
    os << v << ",";
  os << "}";
  return os;
}
template <typename T> ostream &operator<<(ostream &os, set<T> &s) {
  os << "{";
  for (auto p : s)
    os << p << ",";
  os << "}";
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, map<T1, T2> &m) {
  os << "{";
  for (auto p : m)
    os << p << ",";
  os << "}";
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  os << "[" << p.first << " " << p.second << "]";
  return os;
}

int main() {
  int N;
  cin >> N;
  VEC<string> S(N);
  REP(i, 0, N) {
    cin >> S[i];
    sort(ALL(S[i]));
  }
  S.push_back("zzzzzzzzzzzz");
  sort(ALL(S));
  // DUMP(S);
  LL cnt = 0;
  REP(l, 0, N) {
    int r = l + 1;
    while (S[l] == S[r]) {
      r++;
    }
    LL k = r - l;
    cnt += k * (k - 1) / 2;
    l = r - 1;
  }
  cout << cnt << endl;

  return 0;
}