Problem p00348 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define all(c) (c).begin(), (c).end()
#define pb push_back
#define dbg(...)                                                               \\
  do {                                                                         \\
    cerr << __LINE__ << ": ";                                                  \\
    dbgprint(#__VA_ARGS__, __VA_ARGS__);                                       \\
  } while (0);

using namespace std;

namespace std {
template <class S, class T> struct hash<pair<S, T>> {
  size_t operator()(const pair<S, T> &p) const {
    return ((size_t)1e9 + 7) * hash<S>()(p.first) + hash<T>()(p.second);
  }
};
template <class T> struct hash<vector<T>> {
  size_t operator()(const vector<T> &v) const {
    size_t h = 0;
    for (auto i : v)
      h = h * ((size_t)1e9 + 7) + hash<T>()(i) + 1;
    return h;
  }
};
} // namespace std
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "[ ";
  rep(i, v.size()) os << v[i] << (i == v.size() - 1 ? " ]" : ", ");
  return os;
}
template <class T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << "{ ";
  for (const auto &i : v)
    os << i << ", ";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const map<T, U> &v) {
  os << "{";
  for (const auto &i : v)
    os << " " << i.first << ": " << i.second << ",";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
void dbgprint(const string &fmt) { cerr << endl; }
template <class H, class... T>
void dbgprint(const string &fmt, const H &h, const T &...r) {
  cerr << fmt.substr(0, fmt.find(",")) << "= " << h << " ";
  dbgprint(fmt.substr(fmt.find(",") + 1), r...);
}
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pi;
const int inf = (int)1e9;
const double INF = 1e12, EPS = 1e-9;
struct skew_heap {
  struct node {
    node *ch[2];
    int key;
  } *root;
  int size;

  skew_heap() : root(0), size(0) {}
  node *merge(node *a, node *b) {
    if (!a || !b)
      return a ? a : b;
    if (a->key > b->key)
      swap(a, b); // min heap
    a->ch[1] = merge(b, a->ch[1]);
    swap(a->ch[0], a->ch[1]);
    return a;
  }
  void push(int key) {
    node *n = new node();
    n->ch[0] = n->ch[1] = 0;
    n->key = key;
    root = merge(root, n);
    size++;
  }
  void pop() {
    node *temp = root;
    root = merge(root->ch[0], root->ch[1]);
    size--;
  }
  int top() { return root->key; }
  bool empty() { return !root; }
  void merge(skew_heap x) { // destroy x
    root = merge(root, x.root);
    size += x.size;
  }
};
int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  int n;
  cin >> n;
  deque<int> q;
  vector<skew_heap> v;
  {
    vi in, vs;
    rep(i, n) {
      int a;
      cin >> a;
      vs.pb(a);
    }
    in = vs;
    sort(all(vs));
    rep(i, n) {
      v.push_back(skew_heap());
      v.back().push(lower_bound(all(vs), in[i]) - vs.begin());
      q.push_back(i);
    }
  }

  ll ans = 0;
  for (int i = 0;;) {
    int fid = q[0];
    skew_heap &f = v[fid];
    q.pop_front();

    if (f.top() != i) {
      v[q[0]].merge(f);
      continue;
    }

    int s = f.size;
    if (q.size() == 0) {
      ans += s * (s - 1ll) / 2;
      break;
    }

    f.pop();
    ans += s - 1;
    if (s - 1)
      q.push_back(fid);
    i++;
  }
  cout << ans << endl;

  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define all(c) (c).begin(), (c).end()
#define pb push_back
#define dbg(...)                                                               \\
  do {                                                                         \\
    cerr << __LINE__ << ": ";                                                  \\
    dbgprint(#__VA_ARGS__, __VA_ARGS__);                                       \\
  } while (0);

using namespace std;

namespace std {
template <class S, class T> struct hash<pair<S, T>> {
  size_t operator()(const pair<S, T> &p) const {
    return ((size_t)1e9 + 7) * hash<S>()(p.first) + hash<T>()(p.second);
  }
};
template <class T> struct hash<vector<T>> {
  size_t operator()(const vector<T> &v) const {
    size_t h = 0;
    for (auto i : v)
      h = h * ((size_t)1e9 + 7) + hash<T>()(i) + 1;
    return h;
  }
};
} // namespace std
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "[ ";
  rep(i, v.size()) os << v[i] << (i == v.size() - 1 ? " ]" : ", ");
  return os;
}
template <class T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << "{ ";
  for (const auto &i : v)
    os << i << ", ";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const map<T, U> &v) {
  os << "{";
  for (const auto &i : v)
    os << " " << i.first << ": " << i.second << ",";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
void dbgprint(const string &fmt) { cerr << endl; }
template <class H, class... T>
void dbgprint(const string &fmt, const H &h, const T &...r) {
  cerr << fmt.substr(0, fmt.find(",")) << "= " << h << " ";
  dbgprint(fmt.substr(fmt.find(",") + 1), r...);
}
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pi;
const int inf = (int)1e9;
const double INF = 1e12, EPS = 1e-9;
struct skew_heap {
  struct node {
    node *ch[2];
    int key;
  } *root;
  int size;

  skew_heap() : root(0), size(0) {}
  node *merge(node *a, node *b) {
    if (!a || !b)
      return a ? a : b;
    if (a->key > b->key)
      swap(a, b); // min heap
    a->ch[1] = merge(b, a->ch[1]);
    swap(a->ch[0], a->ch[1]);
    return a;
  }
  void push(int key) {
    node *n = new node();
    n->ch[0] = n->ch[1] = 0;
    n->key = key;
    root = merge(root, n);
    size++;
  }
  void pop() {
    node *temp = root;
    root = merge(root->ch[0], root->ch[1]);
    size--;
  }
  int top() { return root->key; }
  bool empty() { return !root; }
  void merge(skew_heap x) { // destroy x
    root = merge(root, x.root);
    size += x.size;
  }
};
int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  int n;
  cin >> n;
  deque<int> q;
  vector<skew_heap> v;
  rep(i, n) {
    int a;
    cin >> a;
    v.push_back(skew_heap());
    v.back().push(a - 1);
    q.push_back(i);
  }

  ll ans = 0;
  for (int i = 0;;) {
    int fid = q[0];
    skew_heap &f = v[fid];
    // dbg(i, q.size(), f.top(), ans);
    q.pop_front();

    if (f.top() != i) {
      v[q[0]].merge(f);
      continue;
    }

    int s = f.size;
    if (q.size() == 0) {
      ans += s * (s - 1ll) / 2;
      break;
    }

    f.pop();
    ans += s - 1;
    if (s - 1)
      q.push_back(fid);
    i++;
  }
  cout << ans << endl;

  return 0;
}