Queue

#include <iostream>
#include <string>
using namespace std;
class Queue {
public:
    Queue() : i_(0U), n_(n), queue_(new int[n_]) {}
    Queue(initializer_list<int> li)
        : i_(li.size()), n_(i_ + n), queue_(new int[n_]) {
        auto beg = queue_;
        for (auto x : li) *beg++ = x;
    }
    Queue(const Queue& q)
        : i_(q.i_), n_(q.n_), queue_(new int[n_]) {
        for (auto i = 0U; i < i_; ++i) queue_[i] = q.queue_[i];
    }
    Queue(Queue&& q) : i_(q.i_), n_(q.n_), queue_(move(q.queue_)) { }
    Queue& operator=(const Queue& q) {
        if (&q != this) {
            i_ = q.i_;
            n_ = q.n_;
            queue_ = new int[n_];
            for (auto i = 0U; i < i_; ++i) queue_[i] = q.queue_[i];
        }
        return *this;
    }
    Queue& operator=(Queue&& q) {
        i_ = q.i_;
        n_ = q.n_;
        queue_ = move(q.queue_);
        return *this;
    }
    ~Queue() {
        if (queue_ != nullptr) {
            delete[] queue_;
            queue_ = nullptr;
        }
    }
    void push(const int value) {
        if (i_ == n_) {
            n_ <<= 1;
            auto tmp = new int[n_];
            for (auto i = 0U; i < i_; ++i) tmp[i] = queue_[i];
            queue_ = move(tmp);
        }
        queue_[i_] = value;
        ++i_;
    }
    void pop() {
        if (i_ == 1U) i_ = 0U;
        else {
            for (auto i = 1U; i < i_; ++i) queue_[i - 1U] = queue_[i];
            --i_;
        }
    }
    int& front() { return *queue_; }
    int& back() { return *(queue_ + i_ - 1); }
    bool empty()const { return 0U == i_; }
    size_t size()const { return i_; }
    size_t capacity()const { return n_; }
    void clear() { i_ = 0U; }
private:
    size_t i_;
    size_t n_;
    int* queue_;
    const static size_t n = 8U;
};
int main() {
    Queue queue({ 1, 2, 3, 4, 5, 6, 7, 8 });
    string ui[] = { "\n - size: ",  "\n - capacity: ", "\n - front: ", "\n - back: " };
    cout << "\tbefore queue.pop():" << ui[0] << queue.size() << ui[1] << queue.capacity();
    if (!queue.empty()) cout << ui[2] << queue.front() << ui[3] << queue.back();
    if (!queue.empty()) queue.pop();
    cout << "\n\tafter queue.pop():" << ui[0] << queue.size() << ui[1] << queue.capacity();
    if (!queue.empty()) cout << ui[2] << queue.front() << ui[3] << queue.back();
    queue.push(1);
    cout << "\n\tafter queue.push(1):" << ui[0] << queue.size() << ui[1] << queue.capacity();
    if (!queue.empty()) cout << ui[2] << queue.front() << ui[3] << queue.back();
    for (auto x = 10; x < 20; ++x) queue.push(x);
    cout << "\n\tafter queue.push(...x):" << ui[0] << queue.size() << ui[1] << queue.capacity();
    if (!queue.empty()) cout << ui[2] << queue.front() << ui[3] << queue.back();
    cout.put('\n');
    cin.get();
}