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- #include <algorithm>
- #include <iostream>
- #include <random>
- #include <string>
- #include <set>
- using namespace std;
- class RandomContainer {
- public:
- void Insert(int val) {
- values_pool_.insert(val);
- }
- void Remove(int val) {
- values_pool_.erase(val);
- }
- bool Has(int val) const {
- return values_pool_.count(val);
- }
- int GetRand() const {
- uniform_int_distribution<int> distr(0, values_pool_.size() - 1);
- int rand_index = distr(engine_);
- return *next(values_pool_.begin(), rand_index);
- }
- private:
- set<int> values_pool_;
- mutable mt19937 engine_;
- };
- int main() {
- RandomContainer container;
- int query_num = 0;
- cin >> query_num;
- for (int query_id = 0; query_id < query_num; query_id++) {
- string query_type;
- cin >> query_type;
- if (query_type == "INSERT"s) {
- int value = 0;
- cin >> value;
- container.Insert(value);
- }
- else if (query_type == "REMOVE"s) {
- int value = 0;
- cin >> value;
- container.Remove(value);
- }
- else if (query_type == "HAS"s) {
- int value = 0;
- cin >> value;
- if (container.Has(value)) {
- cout << "true"s << endl;
- }
- else {
- cout << "false"s << endl;
- }
- }
- else if (query_type == "RAND"s) {
- cout << container.GetRand() << endl;
- }
- }
- }
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