Problem p02456 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <thread>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef unsigned long long int ull;
typedef long long int ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pi;
typedef pair<double, double> pd;
typedef pair<double, ll> pdl;
#define F first
#define S second
const ll E = 1e18 + 7;
const ll MOD = 1000000007;

template <typename T, typename U> class treap {
private:
  struct node {
    ll priority;
    T key;
    U a;
    node *parent;
    node *right;
    node *left;
  };

  random_device r;
  mt19937 mt;
  list<node> tree;
  node *root;
  node leaf = {0, T(), U(), NULL, NULL, NULL};
  ll Size;

  node *search(T key) {
    if (Size == 0) {
      return err();
    }
    node *where = root;
    while (1) {
      if ((*where).key == key) {
        return where;
      }
      if ((*where).right != err() && (*where).key < key) {
        where = (*where).right;
        continue;
      }
      if ((*where).left != err() && key < (*where).key) {
        where = (*where).left;
        continue;
      }
      return where;
    }
    return err();
  }

  node *err() { return &leaf; }

  ll mk_pr() {
    uniform_int_distribution<int> R(1, 1000000000);
    return R(mt);
  }

  void parent_change(node &P, node *from, node *to) {
    if (P.right == from) {
      P.right = to;
      return;
    } else if (P.left == from) {
      P.left = to;
      return;
    }
    assert(false);
  }

  void parent_change(node *P, node *from, node *to) {
    parent_change(*P, from, to);
  }

  node *rotateL(node &where) {
    node *right = where.right;
    assert(right != err());
    node *L = (*right).left;
    if (L != err()) {
      where.right = L;
      (*L).parent = &where;
    } else {
      where.right = err();
    }
    (*right).left = &where;
    if (where.parent == err()) {
      root = right;
      (*right).parent = err();
    } else {
      (*right).parent = where.parent;
      parent_change((*right).parent, &where, right);
    }
    where.parent = right;
    return right;
  }

  node *rotateR(node &where) {
    node *left = where.left;
    assert(left != err());
    node *R = (*left).right;
    if (R != err()) {
      where.left = R;
      (*R).parent = &where;
    } else {
      where.left = err();
    }
    (*left).right = &where;
    if (where.parent == err()) {
      root = left;
      (*left).parent = err();
    } else {
      (*left).parent = where.parent;
      parent_change((*left).parent, &where, left);
    }
    where.parent = left;
    return left;
  }

  node *rotate(node &where) {
    node *P = where.parent;
    if (P != err() && (*P).priority < where.priority) {
      if ((*P).right == &where) {
        rotateL(*P);
      } else {
        rotateR(*P);
      }
    }
    return &where;
  }

  node *rotate(node *where) { return rotate(*where); }

  node *Max(node *where) {
    assert(where != err());
    while (1) {
      if ((*where).right == err()) {
        return where;
      }
      where = (*where).right;
    }
    return err();
  }

  node *Min(node *where) {
    assert(where != err());
    while (1) {
      if ((*where).left == err()) {
        return where;
      }
      where = (*where).left;
    }
    return err();
  }

  node *erase(node *where) {
    if ((*where).right != err() && (*where).left != err()) {
      node *ers = Min((*where).right);
      (*where).key = (*ers).key;
      (*where).a = (*ers).a;
      erase(ers);
      return where;
    }
    node *ret;
    if ((*where).right == err() && (*where).left == err()) {
      if (where == root) {
        root = err();
        return err();
      }
      parent_change((*where).parent, where, err());
      ret = (*where).parent;
    } else if ((*where).right != err()) {
      if (where == root) {
        root = (*where).right;
        (*(*where).right).parent = err();
        return root;
      }
      parent_change((*where).parent, where, (*where).right);
      (*(*where).right).parent = (*where).parent;
      ret = (*where).parent;
    } else {
      if (where == root) {
        root = (*where).left;
        (*(*where).left).parent = err();
        return root;
      }
      parent_change((*where).parent, where, (*where).left);
      (*(*where).left).parent = (*where).parent;
      ret = (*where).parent;
    }
    return ret;
  }

public:
  treap() : mt(r()) {
    Size = 0;
    root = err();
  }

  void insert(T key, U a) {
    if (Size == 0) {
      tree.push_front({mk_pr(), key, a, err(), err(), err()});
      Size++;
      root = &(*tree.begin());
      return;
    }
    node *where = search(key);
    if ((*where).key == key) {
      (*where).a = a;
    } else {
      tree.push_front({mk_pr(), key, a, where, err(), err()});
      node *New = &(*tree.begin());
      if ((*where).key < key) {
        (*where).right = New;
      } else {
        (*where).left = New;
      }
      while (New != err()) {
        New = rotate(New);
        New = (*New).parent;
      }
      Size++;
    }
  }

  U *find(T key) {
    if (Size == 0) {
      return end();
    }
    node *where = search(key);
    if ((*where).key == key) {
      return &(*where).a;
    }
    return end();
  }

  U *end() { return &leaf.a; }

  ll size() { return Size; }

  U *erase(T key) {
    node *where = search(key);
    if ((*where).key != key) {
      return end();
    }
    Size--;
    return &(*erase(where)).a;
  }

  void print() {
    if (Size == 0) {
      return;
    }
    dfs(root);
  }

  void dfs(node *where) {
    assert(where != err());
    cout << (*where).key << " " << (*where).priority << endl;
    if ((*where).right != err()) {
      dfs((*where).right);
    }
    if ((*where).left != err()) {
      dfs((*where).left);
    }
  }

  void test() {
    mid_dfs(root);
    cout << endl;
    first_dfs(root);
    cout << endl;
  }

  void mid_dfs(node *where) {
    assert(where != err());
    if ((*where).left != err()) {
      mid_dfs((*where).left);
    }
    cout << " " << (*where).a;
    if ((*where).right != err()) {
      mid_dfs((*where).right);
    }
  }

  void first_dfs(node *where) {
    assert(where != err());
    cout << " " << (*where).a;
    if ((*where).left != err()) {
      first_dfs((*where).left);
    }
    if ((*where).right != err()) {
      first_dfs((*where).right);
    }
  }
};

int main() {
  treap<ll, ll> T;
  ll q;
  cin >> q;
  while (q--) {
    ll com;
    cin >> com;
    if (com == 0) {
      ll x;
      cin >> x;
      T.insert(x, x);
      cout << T.size() << endl;
    } else if (com == 1) {
      ll x;
      cin >> x;
      if (T.find(x) == T.end()) {
        cout << 0 << endl;
      } else {
        cout << 1 << endl;
      }
    } else {
      ll x;
      cin >> x;
      T.erase(x);
    }
  }

  return 0;
}


Fixed submission:
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <thread>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef unsigned long long int ull;
typedef long long int ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pi;
typedef pair<double, double> pd;
typedef pair<double, ll> pdl;
#define F first
#define S second
const ll E = 1e18 + 7;
const ll MOD = 1000000007;

template <typename T, typename U> class treap {
private:
  struct node {
    ll priority;
    T key;
    U a;
    node *parent;
    node *right;
    node *left;
  };

  random_device r;
  mt19937 mt;
  list<node> tree;
  node *root;
  node leaf = {0, T(), U(), NULL, NULL, NULL};
  ll Size;

  node *search(T key) {
    if (Size == 0) {
      return err();
    }
    node *where = root;
    while (1) {
      if ((*where).key == key) {
        return where;
      }
      if ((*where).right != err() && (*where).key < key) {
        where = (*where).right;
        continue;
      }
      if ((*where).left != err() && key < (*where).key) {
        where = (*where).left;
        continue;
      }
      return where;
    }
    return err();
  }

  node *err() { return &leaf; }

  ll mk_pr() {
    uniform_int_distribution<int> R(1, 1000000000);
    return R(mt);
  }

  void parent_change(node &P, node *from, node *to) {
    if (P.right == from) {
      P.right = to;
      return;
    } else if (P.left == from) {
      P.left = to;
      return;
    }
    assert(false);
  }

  void parent_change(node *P, node *from, node *to) {
    parent_change(*P, from, to);
  }

  node *rotateL(node &where) {
    node *right = where.right;
    assert(right != err());
    node *L = (*right).left;
    if (L != err()) {
      where.right = L;
      (*L).parent = &where;
    } else {
      where.right = err();
    }
    (*right).left = &where;
    if (where.parent == err()) {
      root = right;
      (*right).parent = err();
    } else {
      (*right).parent = where.parent;
      parent_change((*right).parent, &where, right);
    }
    where.parent = right;
    return right;
  }

  node *rotateR(node &where) {
    node *left = where.left;
    assert(left != err());
    node *R = (*left).right;
    if (R != err()) {
      where.left = R;
      (*R).parent = &where;
    } else {
      where.left = err();
    }
    (*left).right = &where;
    if (where.parent == err()) {
      root = left;
      (*left).parent = err();
    } else {
      (*left).parent = where.parent;
      parent_change((*left).parent, &where, left);
    }
    where.parent = left;
    return left;
  }

  node *rotate(node &where) {
    node *P = where.parent;
    if (P != err() && (*P).priority < where.priority) {
      if ((*P).right == &where) {
        rotateL(*P);
      } else {
        rotateR(*P);
      }
    }
    return &where;
  }

  node *rotate(node *where) { return rotate(*where); }

  node *Max(node *where) {
    assert(where != err());
    while (1) {
      if ((*where).right == err()) {
        return where;
      }
      where = (*where).right;
    }
    return err();
  }

  node *Min(node *where) {
    assert(where != err());
    while (1) {
      if ((*where).left == err()) {
        return where;
      }
      where = (*where).left;
    }
    return err();
  }

  node *erase(node *where) {
    if ((*where).right != err() && (*where).left != err()) {
      node *ers = Min((*where).right);
      (*where).key = (*ers).key;
      (*where).a = (*ers).a;
      erase(ers);
      return where;
    }
    node *ret;
    if ((*where).right == err() && (*where).left == err()) {
      if (where == root) {
        root = err();
        return err();
      }
      parent_change((*where).parent, where, err());
      ret = (*where).parent;
    } else if ((*where).right != err()) {
      if (where == root) {
        root = (*where).right;
        (*(*where).right).parent = err();
        return root;
      }
      parent_change((*where).parent, where, (*where).right);
      (*(*where).right).parent = (*where).parent;
      ret = (*where).parent;
    } else {
      if (where == root) {
        root = (*where).left;
        (*(*where).left).parent = err();
        return root;
      }
      parent_change((*where).parent, where, (*where).left);
      (*(*where).left).parent = (*where).parent;
      ret = (*where).parent;
    }
    return ret;
  }

public:
  treap() : mt(r()) {
    Size = 0;
    root = err();
  }

  void insert(T key, U a) {
    if (Size == 0) {
      tree.push_front({mk_pr(), key, a, err(), err(), err()});
      Size++;
      root = &(*tree.begin());
      return;
    }
    node *where = search(key);
    if ((*where).key == key) {
      (*where).a = a;
    } else {
      tree.push_front({mk_pr(), key, a, where, err(), err()});
      node *New = &(*tree.begin());
      if ((*where).key < key) {
        (*where).right = New;
      } else {
        (*where).left = New;
      }
      while (New != err()) {
        New = rotate(New);
        New = (*New).parent;
      }
      Size++;
    }
  }

  U *find(T key) {
    if (Size == 0) {
      return end();
    }
    node *where = search(key);
    if ((*where).key == key) {
      return &(*where).a;
    }
    return end();
  }

  U *end() { return &leaf.a; }

  ll size() { return Size; }

  U *erase(T key) {
    node *where = search(key);
    if (where == err()) {
      return end();
    }
    if ((*where).key != key) {
      return end();
    }
    Size--;
    return &(*erase(where)).a;
  }

  void print() {
    if (Size == 0) {
      return;
    }
    dfs(root);
  }

  void dfs(node *where) {
    assert(where != err());
    cout << (*where).key << " " << (*where).priority << endl;
    if ((*where).right != err()) {
      dfs((*where).right);
    }
    if ((*where).left != err()) {
      dfs((*where).left);
    }
  }

  void test() {
    mid_dfs(root);
    cout << endl;
    first_dfs(root);
    cout << endl;
  }

  void mid_dfs(node *where) {
    assert(where != err());
    if ((*where).left != err()) {
      mid_dfs((*where).left);
    }
    cout << " " << (*where).a;
    if ((*where).right != err()) {
      mid_dfs((*where).right);
    }
  }

  void first_dfs(node *where) {
    assert(where != err());
    cout << " " << (*where).a;
    if ((*where).left != err()) {
      first_dfs((*where).left);
    }
    if ((*where).right != err()) {
      first_dfs((*where).right);
    }
  }
};

int main() {
  treap<ll, ll> T;
  ll q;
  cin >> q;
  while (q--) {
    ll com;
    cin >> com;
    if (com == 0) {
      ll x;
      cin >> x;
      T.insert(x, x);
      cout << T.size() << endl;
    } else if (com == 1) {
      ll x;
      cin >> x;
      if (T.find(x) == T.end()) {
        cout << 0 << endl;
      } else {
        cout << 1 << endl;
      }
    } else {
      ll x;
      cin >> x;
      T.erase(x);
    }
  }

  return 0;
}