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:heavy_check_mark: verify/ds/deque/persistent_deque.test.cpp

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Code

#define PROBLEM "https://judge.yosupo.jp/problem/persistent_queue"

#include "../../../ds/deque/persistent_deque.hpp"
#include "../../../utilities/fast_io.hpp"

#include <cassert>
#include <cstdint>
#include <deque>
#include <memory>
#include <utility>
#include <vector>

namespace {

using Deque = m1une::ds::PersistentDeque<int>;

void assert_ends(const Deque& actual, const std::deque<int>& expected) {
    assert(actual.size() == int(expected.size()));
    assert(actual.empty() == expected.empty());
    if (expected.empty()) return;
    assert(actual.front() == expected.front());
    assert(actual.back() == expected.back());
}

void assert_all(Deque actual, std::deque<int> expected) {
    assert_ends(actual, expected);
    while (!expected.empty()) {
        assert(actual.front() == expected.front());
        actual = actual.pop_front();
        expected.pop_front();
    }
    assert(actual.empty());
}

void test_randomized() {
    std::uint64_t state = 49979687ULL;
    auto random = [&]() {
        state ^= state << 7;
        state ^= state >> 9;
        return state;
    };

    std::vector<std::pair<Deque, std::deque<int>>> versions;
    versions.emplace_back();
    for (int step = 0; step < 10000; step++) {
        int version = int(random() % versions.size());
        const Deque& current = versions[version].first;
        const std::deque<int>& expected = versions[version].second;
        assert_ends(current, expected);

        Deque next = current;
        std::deque<int> next_expected = expected;
        int operation = expected.empty() ? int(random() % 2) : int(random() % 4);
        if (operation == 0) {
            int value = int(random() % 1000000);
            next = current.push_front(value);
            next_expected.push_front(value);
        } else if (operation == 1) {
            int value = int(random() % 1000000);
            next = current.push_back(value);
            next_expected.push_back(value);
        } else if (operation == 2) {
            next = current.pop_front();
            next_expected.pop_front();
        } else {
            next = current.pop_back();
            next_expected.pop_back();
        }

        assert_ends(current, expected);
        assert_ends(next, next_expected);
        if (step % 127 == 0) assert_all(next, next_expected);
        versions.emplace_back(std::move(next), std::move(next_expected));
    }
}

void test_adversarial() {
    Deque deque;
    std::deque<int> expected;
    for (int value = 0; value < 50000; value++) {
        if (value % 2 == 0) {
            deque = deque.push_front(value);
            expected.push_front(value);
        } else {
            deque = deque.push_back(value);
            expected.push_back(value);
        }
        assert_ends(deque, expected);
    }
    for (int step = 0; step < 50000; step++) {
        if (step % 2 == 0) {
            deque = deque.pop_back();
            expected.pop_back();
        } else {
            deque = deque.pop_front();
            expected.pop_front();
        }
        assert_ends(deque, expected);
    }
    assert(deque.empty());

    Deque one_sided;
    for (int value = 0; value < 50000; value++) {
        one_sided = one_sided.push_front(value);
    }
    for (int value = 0; value < 50000; value++) {
        assert(one_sided.back() == value);
        one_sided = one_sided.pop_back();
    }
    assert(one_sided.empty());

    Deque stable = Deque().push_back(4);
    const int& reference = stable.front();
    Deque growing = stable;
    for (int value = 5; value <= 10000; value++) {
        growing = growing.push_front(value).push_back(-value);
    }
    assert(reference == 4);
    assert(growing.front() == 10000);
    assert(growing.back() == -10000);
    assert(stable.front() == 4);
    assert(growing.clear().empty());

    m1une::ds::PersistentDeque<std::unique_ptr<int>> move_only;
    auto first = move_only.push_front(std::make_unique<int>(7));
    auto second = first.push_back(std::make_unique<int>(11));
    auto branch = first.push_front(std::make_unique<int>(3));
    assert(*first.front() == 7);
    assert(*second.back() == 11);
    assert(*second.pop_front().front() == 11);
    assert(*branch.front() == 3);
    assert(*branch.back() == 7);
}

}  // namespace

int main() {
    m1une::utilities::FastInput fast_input;
    m1une::utilities::FastOutput fast_output;

    test_randomized();
    test_adversarial();

    int query_count = 0;
    fast_input >> query_count;
    Deque empty;
    std::vector<Deque> versions(query_count + 1, empty);
    for (int query = 0; query < query_count; query++) {
        int type = 0, base = 0;
        fast_input >> type >> base;
        const Deque& source = versions[base + 1];
        if (type == 0) {
            int value = 0;
            fast_input >> value;
            versions[query + 1] = source.push_back(value);
        } else {
            fast_output << source.front() << '\n';
            versions[query + 1] = source.pop_front();
        }
    }
}
#line 1 "verify/ds/deque/persistent_deque.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/persistent_queue"

#line 1 "ds/deque/persistent_deque.hpp"



#include <cassert>
#include <cstddef>
#include <cstdint>
#include <deque>
#include <memory>
#include <optional>
#include <utility>
#include <vector>

namespace m1une {
namespace ds {

// Okasaki's purely persistent real-time deque.
template <class T>
struct PersistentDeque {
   private:
    static constexpr int balance_factor = 2;

    enum class StreamKind : std::uint8_t {
        cons,
        take,
        rotate_drop,
        rotate_reverse,
    };

    // The three integer fields contain either an evaluated cons cell or the
    // arguments of one incremental stream operation.
    struct StreamNode {
        mutable StreamKind kind;
        mutable int first;
        mutable int second;
        mutable int third;

        StreamNode(
            StreamKind node_kind,
            int first_argument,
            int second_argument,
            int third_argument = -1
        )
            : kind(node_kind),
              first(first_argument),
              second(second_argument),
              third(third_argument) {}
    };

    struct Pool {
        std::deque<std::optional<T>> values;
        std::deque<std::optional<StreamNode>> streams;
        std::vector<int> value_references, stream_references;
        std::vector<int> next_free_value, next_free_stream;
        std::vector<int> unowned_values, unowned_streams;
        int first_free_value = -1;
        int first_free_stream = -1;
        std::size_t live_values = 0;
        std::size_t live_streams = 0;

        void retain_value(int value) {
            if (value != -1) ++value_references[value];
        }

        void release_value(int value) {
            if (value == -1) return;
            assert(values[value].has_value() && value_references[value] > 0);
            if (--value_references[value] != 0) return;
            values[value].reset();
            next_free_value[value] = first_free_value;
            first_free_value = value;
            --live_values;
        }

        void retain_stream(int stream) {
            if (stream != -1) ++stream_references[stream];
        }

        void retain_dependencies(const StreamNode& node) {
            if (node.kind == StreamKind::cons) {
                retain_value(node.first);
                retain_stream(node.second);
            } else if (node.kind == StreamKind::take) {
                retain_stream(node.first);
            } else if (node.kind == StreamKind::rotate_drop) {
                retain_stream(node.first);
                retain_stream(node.third);
            } else {
                retain_stream(node.first);
                retain_stream(node.second);
                retain_stream(node.third);
            }
        }

        void release_zero_stream(int stream) {
            std::vector<int> pending = {stream};
            while (!pending.empty()) {
                int current = pending.back();
                pending.pop_back();
                assert(streams[current].has_value() && stream_references[current] == 0);
                StreamNode node = *streams[current];
                streams[current].reset();
                next_free_stream[current] = first_free_stream;
                first_free_stream = current;
                --live_streams;

                auto release_child = [&](int child) {
                    if (child != -1 && --stream_references[child] == 0) pending.push_back(child);
                };
                if (node.kind == StreamKind::cons) {
                    release_value(node.first);
                    release_child(node.second);
                } else if (node.kind == StreamKind::take) {
                    release_child(node.first);
                } else if (node.kind == StreamKind::rotate_drop) {
                    release_child(node.first);
                    release_child(node.third);
                } else {
                    release_child(node.first);
                    release_child(node.second);
                    release_child(node.third);
                }
            }
        }

        void release_stream(int stream) {
            if (stream == -1) return;
            assert(streams[stream].has_value() && stream_references[stream] > 0);
            if (--stream_references[stream] == 0) release_zero_stream(stream);
        }

        template <class... Args>
        int store_value(Args&&... args) {
            int result;
            if (first_free_value == -1) {
                result = int(values.size());
                values.emplace_back(std::in_place, std::forward<Args>(args)...);
                value_references.push_back(0);
                next_free_value.push_back(-1);
            } else {
                result = first_free_value;
                first_free_value = next_free_value[result];
                values[result].emplace(std::forward<Args>(args)...);
                value_references[result] = 0;
            }
            unowned_values.push_back(result);
            ++live_values;
            return result;
        }

        int make_stream(StreamKind kind, int first, int second, int third) {
            int result;
            if (first_free_stream == -1) {
                result = int(streams.size());
                streams.emplace_back(std::in_place, kind, first, second, third);
                stream_references.push_back(0);
                next_free_stream.push_back(-1);
            } else {
                result = first_free_stream;
                first_free_stream = next_free_stream[result];
                streams[result].emplace(kind, first, second, third);
                stream_references[result] = 0;
            }
            retain_dependencies(*streams[result]);
            unowned_streams.push_back(result);
            ++live_streams;
            return result;
        }

        void set_cons(int stream, int value, int tail) {
            retain_value(value);
            retain_stream(tail);
            StreamNode old = *streams[stream];
            if (old.kind == StreamKind::take) {
                release_stream(old.first);
            } else if (old.kind == StreamKind::rotate_drop) {
                release_stream(old.first);
                release_stream(old.third);
            } else if (old.kind == StreamKind::rotate_reverse) {
                release_stream(old.first);
                release_stream(old.second);
                release_stream(old.third);
            } else {
                release_value(old.first);
                release_stream(old.second);
            }
            StreamNode& node = *streams[stream];
            node.kind = StreamKind::cons;
            node.first = value;
            node.second = tail;
            node.third = -1;
        }

        void discard_unreferenced() {
            while (!unowned_streams.empty()) {
                int stream = unowned_streams.back();
                unowned_streams.pop_back();
                if (streams[stream].has_value() && stream_references[stream] == 0) release_zero_stream(stream);
            }
            while (!unowned_values.empty()) {
                int value = unowned_values.back();
                unowned_values.pop_back();
                if (values[value].has_value() && value_references[value] == 0) {
                    values[value].reset();
                    next_free_value[value] = first_free_value;
                    first_free_value = value;
                    --live_values;
                }
            }
        }

        std::size_t size() const { return live_values + live_streams; }
    };

    int _front_size;
    int _front;
    int _front_schedule;
    int _rear_size;
    int _rear;
    int _rear_schedule;
    std::shared_ptr<Pool> _pool;

    PersistentDeque(
        int front_size,
        int front,
        int front_schedule,
        int rear_size,
        int rear,
        int rear_schedule,
        std::shared_ptr<Pool> pool
    )
        : _front_size(front_size),
          _front(front),
          _front_schedule(front_schedule),
          _rear_size(rear_size),
          _rear(rear),
          _rear_schedule(rear_schedule),
          _pool(std::move(pool)) {
        retain_state();
        _pool->discard_unreferenced();
    }

    void retain_state() const {
        _pool->retain_stream(_front);
        _pool->retain_stream(_front_schedule);
        _pool->retain_stream(_rear);
        _pool->retain_stream(_rear_schedule);
    }

    void release_state() const {
        _pool->release_stream(_front);
        _pool->release_stream(_front_schedule);
        _pool->release_stream(_rear);
        _pool->release_stream(_rear_schedule);
    }

    template <class... Args>
    int store_value(Args&&... args) const {
        return _pool->store_value(std::forward<Args>(args)...);
    }

    int make_stream(
        StreamKind kind,
        int first,
        int second,
        int third = -1
    ) const {
        return _pool->make_stream(kind, first, second, third);
    }

    int make_cons(int value_index, int tail) const {
        return make_stream(StreamKind::cons, value_index, tail);
    }

    int make_take(int count, int stream) const {
        if (count == 0) return -1;
        assert(count > 0 && stream != -1);
        return make_stream(StreamKind::take, stream, count);
    }

    int make_rotate_drop(int rear, int count, int front) const {
        return make_stream(StreamKind::rotate_drop, rear, count, front);
    }

    int make_rotate_reverse(int rear, int front, int accumulator) const {
        return make_stream(
            StreamKind::rotate_reverse,
            rear,
            front,
            accumulator
        );
    }

    void set_cons(int stream, int value_index, int tail) const {
        _pool->set_cons(stream, value_index, tail);
    }

    int stream_head(int stream) const {
        assert(stream != -1);
        force(stream);
        return (*_pool->streams[stream]).first;
    }

    int stream_tail(int stream) const {
        assert(stream != -1);
        force(stream);
        return (*_pool->streams[stream]).second;
    }

    int drop(int stream, int count) const {
        assert(count >= 0);
        while (count > 0) {
            assert(stream != -1);
            stream = stream_tail(stream);
            count--;
        }
        return stream;
    }

    // Reverses a bounded prefix onto accumulator and returns the unconsumed
    // suffix together with the new accumulator.
    std::pair<int, int> reverse_prefix(
        int stream,
        int count,
        int accumulator
    ) const {
        while (count > 0 && stream != -1) {
            int value_index = stream_head(stream);
            stream = stream_tail(stream);
            accumulator = make_cons(value_index, accumulator);
            count--;
        }
        return {stream, accumulator};
    }

    void force(int stream) const {
        assert(stream != -1);
        StreamNode node = *_pool->streams[stream];
        if (node.kind == StreamKind::cons) return;

        if (node.kind == StreamKind::take) {
            int source = node.first;
            int count = node.second;
            assert(source != -1 && count > 0);
            int value_index = stream_head(source);
            int tail = make_take(count - 1, stream_tail(source));
            set_cons(stream, value_index, tail);
            return;
        }

        if (node.kind == StreamKind::rotate_drop) {
            int rear = node.first;
            int count = node.second;
            int front = node.third;
            if (count < balance_factor || rear == -1) {
                assert(count <= balance_factor || rear != -1);
                int result = make_rotate_reverse(
                    rear,
                    drop(front, count),
                    -1
                );
                set_cons(stream, stream_head(result), stream_tail(result));
                return;
            }
            assert(rear != -1);
            int value_index = stream_head(rear);
            int tail = make_rotate_drop(
                stream_tail(rear),
                count - balance_factor,
                drop(front, balance_factor)
            );
            set_cons(stream, value_index, tail);
            return;
        }

        assert(node.kind == StreamKind::rotate_reverse);
        int rear = node.first;
        int front = node.second;
        int accumulator = node.third;
        if (rear == -1) {
            auto [remaining, result] = reverse_prefix(
                front,
                balance_factor + 1,
                accumulator
            );
            assert(remaining == -1 && result != -1);
            set_cons(stream, stream_head(result), stream_tail(result));
            return;
        }

        int value_index = stream_head(rear);
        auto [remaining, next_accumulator] = reverse_prefix(
            front,
            balance_factor,
            accumulator
        );
        int tail = make_rotate_reverse(
            stream_tail(rear),
            remaining,
            next_accumulator
        );
        set_cons(stream, value_index, tail);
    }

    int execute_once(int schedule) const {
        return schedule == -1 ? -1 : stream_tail(schedule);
    }

    int execute_twice(int schedule) const {
        return execute_once(execute_once(schedule));
    }

    PersistentDeque check(
        int front_size,
        int front,
        int front_schedule,
        int rear_size,
        int rear,
        int rear_schedule
    ) const {
        if (front_size > balance_factor * rear_size + 1) {
            int next_front_size = (front_size + rear_size) / 2;
            int next_rear_size = front_size + rear_size - next_front_size;
            int next_front = make_take(next_front_size, front);
            int next_rear = make_rotate_drop(
                rear,
                next_front_size,
                front
            );
            return PersistentDeque(
                next_front_size,
                next_front,
                next_front,
                next_rear_size,
                next_rear,
                next_rear,
                _pool
            );
        }

        if (rear_size > balance_factor * front_size + 1) {
            int next_front_size = (front_size + rear_size) / 2;
            int next_rear_size = front_size + rear_size - next_front_size;
            int next_front = make_rotate_drop(
                front,
                next_rear_size,
                rear
            );
            int next_rear = make_take(next_rear_size, rear);
            return PersistentDeque(
                next_front_size,
                next_front,
                next_front,
                next_rear_size,
                next_rear,
                next_rear,
                _pool
            );
        }

        return PersistentDeque(
            front_size,
            front,
            front_schedule,
            rear_size,
            rear,
            rear_schedule,
            _pool
        );
    }

   public:
    PersistentDeque()
        : _front_size(0),
          _front(-1),
          _front_schedule(-1),
          _rear_size(0),
          _rear(-1),
          _rear_schedule(-1),
          _pool(std::make_shared<Pool>()) {}

    PersistentDeque(const PersistentDeque& other)
        : _front_size(other._front_size),
          _front(other._front),
          _front_schedule(other._front_schedule),
          _rear_size(other._rear_size),
          _rear(other._rear),
          _rear_schedule(other._rear_schedule),
          _pool(other._pool) {
        if (_pool) retain_state();
    }

    PersistentDeque(PersistentDeque&& other) noexcept
        : _front_size(other._front_size),
          _front(other._front),
          _front_schedule(other._front_schedule),
          _rear_size(other._rear_size),
          _rear(other._rear),
          _rear_schedule(other._rear_schedule),
          _pool(std::move(other._pool)) {
        other._front_size = other._rear_size = 0;
        other._front = other._front_schedule = other._rear = other._rear_schedule = -1;
    }

    PersistentDeque& operator=(const PersistentDeque& other) {
        if (this == &other) return *this;
        if (other._pool) other.retain_state();
        if (_pool) release_state();
        _front_size = other._front_size;
        _front = other._front;
        _front_schedule = other._front_schedule;
        _rear_size = other._rear_size;
        _rear = other._rear;
        _rear_schedule = other._rear_schedule;
        _pool = other._pool;
        return *this;
    }

    PersistentDeque& operator=(PersistentDeque&& other) noexcept {
        if (this == &other) return *this;
        if (_pool) release_state();
        _front_size = other._front_size;
        _front = other._front;
        _front_schedule = other._front_schedule;
        _rear_size = other._rear_size;
        _rear = other._rear;
        _rear_schedule = other._rear_schedule;
        _pool = std::move(other._pool);
        other._front_size = other._rear_size = 0;
        other._front = other._front_schedule = other._rear = other._rear_schedule = -1;
        return *this;
    }

    ~PersistentDeque() {
        if (_pool) release_state();
    }

    int size() const {
        return _front_size + _rear_size;
    }

    bool empty() const {
        return size() == 0;
    }

    void release() {
        if (_pool) release_state();
        _front_size = _rear_size = 0;
        _front = _front_schedule = _rear = _rear_schedule = -1;
        _pool = std::make_shared<Pool>();
    }

    std::size_t node_count() const { return _pool ? _pool->size() : 0; }

    const T& front() const {
        assert(!empty());
        int stream = _front == -1 ? _rear : _front;
        int value = stream_head(stream);
        _pool->discard_unreferenced();
        return *_pool->values[value];
    }

    const T& back() const {
        assert(!empty());
        int stream = _rear == -1 ? _front : _rear;
        int value = stream_head(stream);
        _pool->discard_unreferenced();
        return *_pool->values[value];
    }

    PersistentDeque push_front(T value) const {
        return emplace_front(std::move(value));
    }

    template <class... Args>
    PersistentDeque emplace_front(Args&&... args) const {
        int value_index = store_value(std::forward<Args>(args)...);
        return check(
            _front_size + 1,
            make_cons(value_index, _front),
            execute_once(_front_schedule),
            _rear_size,
            _rear,
            execute_once(_rear_schedule)
        );
    }

    PersistentDeque push_back(T value) const {
        return emplace_back(std::move(value));
    }

    template <class... Args>
    PersistentDeque emplace_back(Args&&... args) const {
        int value_index = store_value(std::forward<Args>(args)...);
        return check(
            _front_size,
            _front,
            execute_once(_front_schedule),
            _rear_size + 1,
            make_cons(value_index, _rear),
            execute_once(_rear_schedule)
        );
    }

    PersistentDeque pop_front() const {
        assert(!empty());
        if (size() == 1) return clear();
        assert(_front != -1);
        return check(
            _front_size - 1,
            stream_tail(_front),
            execute_twice(_front_schedule),
            _rear_size,
            _rear,
            execute_twice(_rear_schedule)
        );
    }

    PersistentDeque pop_back() const {
        assert(!empty());
        if (size() == 1) return clear();
        assert(_rear != -1);
        return check(
            _front_size,
            _front,
            execute_twice(_front_schedule),
            _rear_size - 1,
            stream_tail(_rear),
            execute_twice(_rear_schedule)
        );
    }

    PersistentDeque clear() const {
        return PersistentDeque(0, -1, -1, 0, -1, -1, _pool);
    }
};

}  // namespace ds
}  // namespace m1une


#line 1 "utilities/fast_io.hpp"



#include <algorithm>
#include <array>
#include <cerrno>
#include <charconv>
#line 9 "utilities/fast_io.hpp"
#include <cstdio>
#include <cstdlib>
#line 12 "utilities/fast_io.hpp"
#include <cstring>
#include <iterator>
#include <string>
#include <sys/stat.h>
#include <type_traits>
#line 18 "utilities/fast_io.hpp"
#include <unistd.h>
#line 20 "utilities/fast_io.hpp"

namespace m1une {
namespace utilities {

struct FastOutput;

namespace internal {

// Shared with the convenience helpers in template.hpp.
inline FastOutput* standard_output_instance = nullptr;

// Detect std::begin(x), std::end(x).
template <class T, class = void>
struct is_range : std::false_type {};

template <class T>
struct is_range<T, std::void_t<
    decltype(std::begin(std::declval<T&>())),
    decltype(std::end(std::declval<T&>()))
>> : std::true_type {};

template <class T>
inline constexpr bool is_range_v = is_range<T>::value;

template <class T>
using range_reference_t = decltype(*std::begin(std::declval<T&>()));

template <class T>
using range_value_t = std::remove_cv_t<std::remove_reference_t<range_reference_t<T>>>;

template <class T, class = void>
struct range_stored_value {
    using type = range_value_t<T>;
};

template <class T>
struct range_stored_value<T, std::void_t<typename std::remove_cv_t<std::remove_reference_t<T>>::value_type>> {
    using type = typename std::remove_cv_t<std::remove_reference_t<T>>::value_type;
};

template <class T>
using range_stored_value_t = typename range_stored_value<T>::type;

// Treat strings and C strings as scalar output objects, not as ranges.
template <class T>
struct is_char_array : std::false_type {};

template <class T, std::size_t N>
struct is_char_array<T[N]>
    : std::bool_constant<std::is_same_v<std::remove_cv_t<T>, char>> {};

template <class T>
struct is_string_like
    : std::bool_constant<
          std::is_same_v<std::decay_t<T>, std::string>
          || std::is_same_v<std::decay_t<T>, const char*>
          || std::is_same_v<std::decay_t<T>, char*>
          || is_char_array<std::remove_reference_t<T>>::value
      > {};

template <class T>
inline constexpr bool is_string_like_v = is_string_like<T>::value;

// ModInt-like type: x.val() is printable, and x can be assigned from long long.
template <class T, class = void>
struct has_val_method : std::false_type {};

template <class T>
struct has_val_method<T, std::void_t<decltype(std::declval<const T&>().val())>>
    : std::true_type {};

template <class T>
inline constexpr bool has_val_method_v = has_val_method<T>::value;

template <class T, class = void>
struct has_static_mod_raw : std::false_type {};

template <class T>
struct has_static_mod_raw<
    T, std::void_t<decltype(T::mod()), decltype(T::raw(std::declval<uint32_t>()))>>
    : std::true_type {};

template <class T>
inline constexpr bool has_static_mod_raw_v = has_static_mod_raw<T>::value;

// libstdc++ before GCC 16 does not classify __int128 as an integral type in
// strict ISO modes such as -std=c++23. Keep the fast-I/O interface independent
// of that implementation detail.
template <class T>
inline constexpr bool is_integral_v =
    std::is_integral_v<T>
    || std::is_same_v<std::remove_cv_t<T>, __int128_t>
    || std::is_same_v<std::remove_cv_t<T>, __uint128_t>;

template <class T>
inline constexpr bool is_signed_v =
    std::is_signed_v<T>
    || std::is_same_v<std::remove_cv_t<T>, __int128_t>;

template <class T>
struct make_unsigned {
    using type = std::make_unsigned_t<T>;
};

template <>
struct make_unsigned<__int128_t> {
    using type = __uint128_t;
};

template <>
struct make_unsigned<__uint128_t> {
    using type = __uint128_t;
};

template <class T>
using make_unsigned_t = typename make_unsigned<std::remove_cv_t<T>>::type;

}  // namespace internal

struct FastInput {
    static constexpr int buffer_size = 1 << 20;

   private:
    std::FILE* _stream;
    char _buffer[buffer_size];
    int _position;
    int _length;
    int _file_descriptor;
    bool _streaming;

    bool refill() {
        _position = 0;
        if (_streaming) {
            ssize_t length;
            do {
                length = ::read(_file_descriptor, _buffer, buffer_size);
            } while (length < 0 && errno == EINTR);
            if (length <= 0) {
                _length = 0;
                return false;
            }
            _length = int(length);
        } else {
            _length = int(std::fread(_buffer, 1, buffer_size, _stream));
        }
        return _length != 0;
    }

    template <class T>
    bool read_integer_from_stream(T& value) {
        if (!skip_spaces()) return false;
        int c = read_char_raw();

        bool negative = false;
        if (c == '-') {
            negative = true;
            c = read_char_raw();
        }

        if constexpr (internal::is_signed_v<T>) {
            T result = 0;
            while ('0' <= c && c <= '9') {
                result = negative ? result * 10 - (c - '0')
                                  : result * 10 + (c - '0');
                c = read_char_raw();
            }
            value = result;
        } else {
            T result = 0;
            while ('0' <= c && c <= '9') {
                result = result * 10 + T(c - '0');
                c = read_char_raw();
            }
            value = negative ? T(0) - result : result;
        }
        return true;
    }

    bool prepare_number() {
        if (_length - _position >= 64) return true;
        const int remaining = _length - _position;
        if (remaining > 0) std::memmove(_buffer, _buffer + _position, remaining);
        const int added = int(std::fread(_buffer + remaining, 1, buffer_size - remaining, _stream));
        _position = 0;
        _length = remaining + added;
        if (_length < buffer_size) _buffer[_length] = '\0';
        return _length != 0;
    }

   public:
    explicit FastInput(std::FILE* stream = stdin)
        : _stream(stream),
          _position(0),
          _length(0),
          _file_descriptor(::fileno(stream)),
          _streaming([&] {
              struct stat status;
              return _file_descriptor >= 0
                     && ::fstat(_file_descriptor, &status) == 0
                     && !S_ISREG(status.st_mode);
          }()) {}

    FastInput(const FastInput&) = delete;
    FastInput& operator=(const FastInput&) = delete;

    int read_char_raw() {
        if (_position == _length && !refill()) return EOF;
        return _buffer[_position++];
    }

    bool skip_spaces() {
        int c = read_char_raw();
        while (c != EOF && c <= ' ') c = read_char_raw();
        if (c == EOF) return false;
        --_position;
        return true;
    }

    bool read(char& value) {
        if (!skip_spaces()) return false;
        value = char(read_char_raw());
        return true;
    }

    bool read(std::string& value) {
        if (!skip_spaces()) return false;
        value.clear();
        while (true) {
            const int begin = _position;
            while (_position < _length &&
                   static_cast<unsigned char>(_buffer[_position]) > ' ') {
                ++_position;
            }
            value.append(_buffer + begin, _position - begin);
            if (_position < _length) {
                ++_position;
                return true;
            }
            if (!refill()) return true;
        }
    }

    bool read(bool& value) {
        int x;
        if (!read(x)) return false;
        value = x != 0;
        return true;
    }

    template <class T>
    std::enable_if_t<
        internal::is_integral_v<T>
            && !std::is_same_v<std::remove_cv_t<T>, bool>
            && !std::is_same_v<std::remove_cv_t<T>, char>,
        bool
    >
    read(T& value) {
        if (_streaming) return read_integer_from_stream(value);
        if (!prepare_number()) return false;
        int c = static_cast<unsigned char>(_buffer[_position++]);
        while (c <= ' ') c = static_cast<unsigned char>(_buffer[_position++]);

        bool negative = false;
        if (c == '-') {
            negative = true;
            c = static_cast<unsigned char>(_buffer[_position++]);
        }

        if constexpr (internal::is_signed_v<T>) {
            T result = 0;
            while ('0' <= c && c <= '9') {
                const int first = c - '0';
                const int second = static_cast<unsigned char>(_buffer[_position]) - '0';
                if (0 <= second && second <= 9) {
                    result = negative ? result * 100 - (first * 10 + second)
                                      : result * 100 + (first * 10 + second);
                    ++_position;
                } else {
                    result = negative ? result * 10 - first : result * 10 + first;
                }
                c = static_cast<unsigned char>(_buffer[_position++]);
            }
            value = result;
        } else {
            T result = 0;
            while ('0' <= c && c <= '9') {
                const unsigned first = unsigned(c - '0');
                const int second = static_cast<unsigned char>(_buffer[_position]) - '0';
                if (0 <= second && second <= 9) {
                    result = result * 100 + T(first * 10 + unsigned(second));
                    ++_position;
                } else {
                    result = result * 10 + T(first);
                }
                c = static_cast<unsigned char>(_buffer[_position++]);
            }
            value = negative ? T(0) - result : result;
        }
        if (_position > _length) _position = _length;
        return true;
    }

    template <class T>
    std::enable_if_t<std::is_floating_point_v<T>, bool>
    read(T& value) {
        if (!skip_spaces()) return false;
        int c = read_char_raw();
        bool negative = false;
        if (c == '-' || c == '+') {
            negative = c == '-';
            c = read_char_raw();
        }

        long double result = 0;
        while ('0' <= c && c <= '9') {
            result = result * 10 + (c - '0');
            c = read_char_raw();
        }
        if (c == '.') {
            long double place = 0.1L;
            c = read_char_raw();
            while ('0' <= c && c <= '9') {
                result += (c - '0') * place;
                place *= 0.1L;
                c = read_char_raw();
            }
        }
        if (c == 'e' || c == 'E') {
            c = read_char_raw();
            bool exponent_negative = false;
            if (c == '-' || c == '+') {
                exponent_negative = c == '-';
                c = read_char_raw();
            }
            int exponent = 0;
            while ('0' <= c && c <= '9') {
                exponent = exponent * 10 + (c - '0');
                c = read_char_raw();
            }
            long double scale = 1;
            long double power = 10;
            while (exponent > 0) {
                if (exponent & 1) scale *= power;
                power *= power;
                exponent >>= 1;
            }
            result = exponent_negative ? result / scale : result * scale;
        }
        value = static_cast<T>(negative ? -result : result);
        return true;
    }

    template <class T>
    std::enable_if_t<
        internal::has_val_method_v<T>
            && !internal::is_integral_v<T>
            && !internal::is_range_v<T>,
        bool
    >
    read(T& value) {
        long long x;
        if (!read(x)) return false;
        if constexpr (internal::has_static_mod_raw_v<T>) {
            if (x >= 0 && uint64_t(x) < uint64_t(T::mod())) {
                value = T::raw(uint32_t(x));
            } else {
                value = T(x);
            }
        } else {
            value = T(x);
        }
        return true;
    }

    template <class First, class Second>
    bool read(std::pair<First, Second>& value) {
        if (!read(value.first)) return false;
        return read(value.second);
    }

    template <class Range>
    std::enable_if_t<
        internal::is_range_v<Range>
            && !internal::is_string_like_v<Range>,
        bool
    >
    read(Range& range) {
        using StoredValue = internal::range_stored_value_t<Range>;
        constexpr bool nested = internal::is_range_v<StoredValue>
                                && !internal::is_string_like_v<StoredValue>;

        for (auto&& value : range) {
            if constexpr (std::is_same_v<StoredValue, bool> && !nested) {
                bool x;
                if (!read(x)) return false;
                value = x;
            } else {
                if (!read(value)) return false;
            }
        }
        return true;
    }

    template <class First, class Second, class... Rest>
    bool read(First& first, Second& second, Rest&... rest) {
        if (!read(first)) return false;
        return read(second, rest...);
    }

    template <class T>
    FastInput& operator>>(T& value) {
        if (!read(value)) std::abort();
        return *this;
    }
};

struct FastOutput {
    static constexpr int buffer_size = 1 << 20;

   private:
    inline static const auto digit_quads = [] {
        std::array<char, 40000> result{};
        for (int i = 0; i < 10000; i++) {
            int value = i;
            for (int j = 3; j >= 0; j--) {
                result[4 * i + j] = char('0' + value % 10);
                value /= 10;
            }
        }
        return result;
    }();

    std::FILE* _stream;
    char _buffer[buffer_size];
    int _position;
    int _precision;
    std::chars_format _float_format;
    char _range_separator;
    std::string* _capture = nullptr;

    template <class T>
    std::string format_cell(const T& value) {
        std::string result;
        struct CaptureGuard {
            std::string*& target;
            std::string* previous;
            ~CaptureGuard() { target = previous; }
        } guard{_capture, _capture};
        _capture = &result;
        write(value);
        return result;
    }

    template <class Matrix>
    void write_aligned_matrix(const Matrix& matrix) {
        std::vector<std::vector<std::string>> rows;
        std::vector<std::size_t> widths;
        for (const auto& row : matrix) {
            auto& cells = rows.emplace_back();
            std::size_t column = 0;
            for (const auto& value : row) {
                cells.push_back(format_cell(value));
                if (column == widths.size()) widths.push_back(0);
                widths[column] = std::max(widths[column], cells.back().size());
                ++column;
            }
        }
        bool first = true;
        for (const auto& row : rows) {
            if (!first) write_char('\n');
            first = false;
            for (std::size_t column = 0; column < row.size(); ++column) {
                if (column != 0) write_char(_range_separator);
                for (std::size_t padding = row[column].size();
                     padding < widths[column]; ++padding) {
                    write_char(' ');
                }
                write(row[column]);
            }
        }
    }

   public:
    explicit FastOutput(std::FILE* stream = stdout)
        : _stream(stream),
          _position(0),
          _precision(6),
          _float_format(std::chars_format::general),
          _range_separator(' ') {
        if (_stream == stdout
            && internal::standard_output_instance == nullptr) {
            internal::standard_output_instance = this;
        }
    }

    FastOutput(const FastOutput&) = delete;
    FastOutput& operator=(const FastOutput&) = delete;

    ~FastOutput() {
        flush();
        if (internal::standard_output_instance == this) {
            internal::standard_output_instance = nullptr;
        }
    }

    void flush() {
        if (_position != 0) {
            std::fwrite(_buffer, 1, _position, _stream);
            _position = 0;
        }
        std::fflush(_stream);
    }

    void write_char(char c) {
        if (_capture != nullptr) {
            _capture->push_back(c);
            return;
        }
        if (_position == buffer_size) flush();
        _buffer[_position++] = c;
    }

    void write(const char* s) {
        while (*s != '\0') write_char(*s++);
    }

    void write(const std::string& s) {
        if (_capture != nullptr) {
            _capture->append(s);
            return;
        }
        std::size_t position = 0;
        while (position < s.size()) {
            if (_position == buffer_size) flush();
            const std::size_t copied =
                std::min<std::size_t>(buffer_size - _position, s.size() - position);
            std::memcpy(_buffer + _position, s.data() + position, copied);
            _position += int(copied);
            position += copied;
        }
    }

    void write(char c) {
        write_char(c);
    }

    void write(bool value) {
        write_char(value ? '1' : '0');
    }

    template <class T>
    std::enable_if_t<std::is_floating_point_v<T>>
    write(T value) {
        char digits[128];
        auto [end, error] = std::to_chars(
            digits,
            digits + sizeof(digits),
            value,
            _float_format,
            _precision
        );
        if (error != std::errc()) std::abort();
        for (const char* pointer = digits; pointer != end; pointer++) {
            write_char(*pointer);
        }
    }

    template <class T>
    std::enable_if_t<
        internal::is_integral_v<T>
            && !std::is_same_v<std::remove_cv_t<T>, bool>
            && !std::is_same_v<std::remove_cv_t<T>, char>
    >
    write(T value) {
        using Raw = std::remove_cv_t<T>;
        using Unsigned = internal::make_unsigned_t<Raw>;

        Unsigned magnitude;
        if constexpr (internal::is_signed_v<Raw>) {
            if (value < 0) {
                write_char('-');
                magnitude = Unsigned(0) - Unsigned(value);
            } else {
                magnitude = Unsigned(value);
            }
        } else {
            magnitude = value;
        }

        if (magnitude == 0) {
            write_char('0');
            return;
        }

        unsigned chunks[16];
        int count = 0;
        while (magnitude >= 10000) {
            const Unsigned quotient = magnitude / 10000;
            chunks[count++] = unsigned(magnitude - quotient * 10000);
            magnitude = quotient;
        }
        if (_capture == nullptr && _position > buffer_size - 64) flush();
        char captured[64];
        char* const begin = _capture != nullptr ? captured : _buffer + _position;
        char* destination = begin;
        const unsigned leading = unsigned(magnitude);
        const char* first = digit_quads.data() + 4 * leading;
        int skip = leading < 10 ? 3 : leading < 100 ? 2 : leading < 1000 ? 1 : 0;
        for (; skip < 4; skip++) *destination++ = first[skip];
        while (count--) {
            const char* digits = digit_quads.data() + 4 * chunks[count];
            std::memcpy(destination, digits, 4);
            destination += 4;
        }
        if (_capture != nullptr) {
            _capture->append(begin, destination - begin);
        } else {
            _position += int(destination - begin);
        }
    }

    template <class T>
    std::enable_if_t<
        internal::has_val_method_v<T>
            && !internal::is_integral_v<T>
            && !internal::is_range_v<T>
    >
    write(const T& value) {
        write(value.val());
    }

    template <class First, class Second>
    void write(const std::pair<First, Second>& value) {
        write(value.first);
        write_char(' ');
        write(value.second);
    }

    template <class Range>
    std::enable_if_t<
        internal::is_range_v<Range>
            && !internal::is_string_like_v<Range>
    >
    write(const Range& range) {
        using StoredValue = internal::range_stored_value_t<const Range>;
        constexpr bool nested = internal::is_range_v<StoredValue>
                                && !internal::is_string_like_v<StoredValue>;

        bool first = true;
        for (const auto& value : range) {
            if (!first) write_char(nested ? '\n' : _range_separator);
            first = false;
            if constexpr (std::is_same_v<StoredValue, bool> && !nested) {
                write(static_cast<bool>(value));
            } else {
                write(value);
            }
        }
    }

    template <class First, class... Rest>
    void print(const First& first, const Rest&... rest) {
        write(first);
        ((write_char(' '), write(rest)), ...);
    }

    void println() {
        write_char('\n');
    }

    void set_precision(int precision) {
        _precision = precision;
    }

    void set_fixed(int precision = 6) {
        _float_format = std::chars_format::fixed;
        _precision = precision;
    }

    void set_general(int precision = 6) {
        _float_format = std::chars_format::general;
        _precision = precision;
    }

    void set_range_separator(char separator) {
        _range_separator = separator;
    }

    template <class Matrix>
    void write_aligned(const Matrix& matrix) {
        using Row = internal::range_stored_value_t<const Matrix>;
        using Cell = internal::range_stored_value_t<const Row>;
        static_assert(internal::is_range_v<Row> && !internal::is_string_like_v<Row>,
                      "write_aligned requires a two-dimensional range");
        static_assert(!internal::is_range_v<Cell> || internal::is_string_like_v<Cell>,
                      "write_aligned requires scalar cells");
        write_aligned_matrix(matrix);
    }

    template <class Matrix>
    void println_aligned(const Matrix& matrix) {
        write_aligned(matrix);
        write_char('\n');
    }

    template <class... Args>
    void println(const Args&... args) {
        print(args...);
        write_char('\n');
    }

    template <class T>
    FastOutput& operator<<(const T& value) {
        write(value);
        return *this;
    }
};

}  // namespace utilities
}  // namespace m1une


#line 5 "verify/ds/deque/persistent_deque.test.cpp"

#line 12 "verify/ds/deque/persistent_deque.test.cpp"

namespace {

using Deque = m1une::ds::PersistentDeque<int>;

void assert_ends(const Deque& actual, const std::deque<int>& expected) {
    assert(actual.size() == int(expected.size()));
    assert(actual.empty() == expected.empty());
    if (expected.empty()) return;
    assert(actual.front() == expected.front());
    assert(actual.back() == expected.back());
}

void assert_all(Deque actual, std::deque<int> expected) {
    assert_ends(actual, expected);
    while (!expected.empty()) {
        assert(actual.front() == expected.front());
        actual = actual.pop_front();
        expected.pop_front();
    }
    assert(actual.empty());
}

void test_randomized() {
    std::uint64_t state = 49979687ULL;
    auto random = [&]() {
        state ^= state << 7;
        state ^= state >> 9;
        return state;
    };

    std::vector<std::pair<Deque, std::deque<int>>> versions;
    versions.emplace_back();
    for (int step = 0; step < 10000; step++) {
        int version = int(random() % versions.size());
        const Deque& current = versions[version].first;
        const std::deque<int>& expected = versions[version].second;
        assert_ends(current, expected);

        Deque next = current;
        std::deque<int> next_expected = expected;
        int operation = expected.empty() ? int(random() % 2) : int(random() % 4);
        if (operation == 0) {
            int value = int(random() % 1000000);
            next = current.push_front(value);
            next_expected.push_front(value);
        } else if (operation == 1) {
            int value = int(random() % 1000000);
            next = current.push_back(value);
            next_expected.push_back(value);
        } else if (operation == 2) {
            next = current.pop_front();
            next_expected.pop_front();
        } else {
            next = current.pop_back();
            next_expected.pop_back();
        }

        assert_ends(current, expected);
        assert_ends(next, next_expected);
        if (step % 127 == 0) assert_all(next, next_expected);
        versions.emplace_back(std::move(next), std::move(next_expected));
    }
}

void test_adversarial() {
    Deque deque;
    std::deque<int> expected;
    for (int value = 0; value < 50000; value++) {
        if (value % 2 == 0) {
            deque = deque.push_front(value);
            expected.push_front(value);
        } else {
            deque = deque.push_back(value);
            expected.push_back(value);
        }
        assert_ends(deque, expected);
    }
    for (int step = 0; step < 50000; step++) {
        if (step % 2 == 0) {
            deque = deque.pop_back();
            expected.pop_back();
        } else {
            deque = deque.pop_front();
            expected.pop_front();
        }
        assert_ends(deque, expected);
    }
    assert(deque.empty());

    Deque one_sided;
    for (int value = 0; value < 50000; value++) {
        one_sided = one_sided.push_front(value);
    }
    for (int value = 0; value < 50000; value++) {
        assert(one_sided.back() == value);
        one_sided = one_sided.pop_back();
    }
    assert(one_sided.empty());

    Deque stable = Deque().push_back(4);
    const int& reference = stable.front();
    Deque growing = stable;
    for (int value = 5; value <= 10000; value++) {
        growing = growing.push_front(value).push_back(-value);
    }
    assert(reference == 4);
    assert(growing.front() == 10000);
    assert(growing.back() == -10000);
    assert(stable.front() == 4);
    assert(growing.clear().empty());

    m1une::ds::PersistentDeque<std::unique_ptr<int>> move_only;
    auto first = move_only.push_front(std::make_unique<int>(7));
    auto second = first.push_back(std::make_unique<int>(11));
    auto branch = first.push_front(std::make_unique<int>(3));
    assert(*first.front() == 7);
    assert(*second.back() == 11);
    assert(*second.pop_front().front() == 11);
    assert(*branch.front() == 3);
    assert(*branch.back() == 7);
}

}  // namespace

int main() {
    m1une::utilities::FastInput fast_input;
    m1une::utilities::FastOutput fast_output;

    test_randomized();
    test_adversarial();

    int query_count = 0;
    fast_input >> query_count;
    Deque empty;
    std::vector<Deque> versions(query_count + 1, empty);
    for (int query = 0; query < query_count; query++) {
        int type = 0, base = 0;
        fast_input >> type >> base;
        const Deque& source = versions[base + 1];
        if (type == 0) {
            int value = 0;
            fast_input >> value;
            versions[query + 1] = source.push_back(value);
        } else {
            fast_output << source.front() << '\n';
            versions[query + 1] = source.pop_front();
        }
    }
}
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