queue

template <typename A> class my_queue {
private:
    A *q;
    int l, r;
    int q_size;
public:
    my_queue(int n) {
        q = new A[2 * n];
        l = r = 0;
        q_size = 2 * n;
    }
    my_queue() {
        q = new A[maxn];
        l = r = 0;
        q_size = maxn;
    }
    ~my_queue() {
        delete[] q;
    }
    void push(A x) {
        if (r == q_size) {
            A *new_q = new A[2 * q_size];
            for (int i = 0; i < q_size; ++i)
                new_q[i] = q[i];
            delete[] q;
            q = new_q;
            q_size *= 2;
        }
        q[r++] = x;
    }
    A front() {
        return q[l];
    }
    void pop() {
        l++;
        if (l == r)
            l = r = 0;
    }
    bool empty()
    {
        return l == r;
    }
    int size() {
        return r - l;
    }
    void clear()
    {
        l = r = 0;
    }
    friend ostream &operator << (ostream &out, const my_queue<A> &q);
};

template <typename A>
ostream &operator << (ostream &out, const my_queue<A> &q){
    for (int i = q.l; i < q.r; i++)
        out << q.q[i] << " ";
    return out;
}