#include <cstdlib>
#include <ctime>
#include <unordered_map>
#include <vector>

class RandomizedSet {
 public:
  RandomizedSet() {
    srand(time(nullptr));
  }

  bool insert(int val) {
    if (map.find(val) != map.end()) return false;
    map[val] = list.size();
    list.push_back(val);
    return true;
  }

  bool remove(int val) {
    auto it = map.find(val);
    if (it == map.end()) return false;
    int idx = it->second;
    int lastVal = list.back();
    list[idx] = lastVal;
    map[lastVal] = idx;
    list.pop_back();
    map.erase(it);
    return true;
  }

  int getRandom() {
    return list[rand() % list.size()];
  }

 private:
  std::vector<int> list;
  std::unordered_map<int, int> map;
};