Question

初学者，用c#怎样实现队列

Answer 1

    /// <summary>
    /// 环形队列
    /// </summary>
    public class MyQueue<T>
    {
        private T[] _array; // 队列容器
        private int _head;  // 队头指针
        private int _tail;  // 队尾指针
        private int _size;  // 容器大小
        private const int increment = 5;  // 队列增量
        static T[] _emptyArray = new T[0];
        public MyQueue()
        {
            _array = _emptyArray;
        }
        public MyQueue(int capacity)
        {
            if (capacity < 0) throw new ArgumentOutOfRangeException("capacity");

            _array = new T[capacity];
            _head = 0;
            _tail = 0;
            _size = 0;
        }

        /// <summary>
        /// 队列元素数目
        /// </summary>
        public int Count { get { return _size; } }

        /// <summary>
        /// 入队
        /// </summary>
        /// <param name="item">队列元素</param>
        public void Enqueue(T item)
        {
            if (_size == _array.Length)
            {
                SetCapacity(_size + increment);
            }

            _array[_tail] = item;
            _tail = (_tail + 1) % _array.Length;
            _size++;
        }

        /// <summary>
        /// 出队
        /// </summary>
        /// <returns></returns>
        public T Dequeue()
        {
            if (_size == 0) throw new InvalidOperationException("空队列");

            T removed = _array[_head];
            _array[_head] = default(T);
            _head = (_head + 1) % _array.Length;
            _size--;

            return removed;
        }

        /// <summary>
        /// 动态调整队列大小
        /// </summary>
        /// <param name="capacity"></param>
        private void SetCapacity(int capacity)
        {
            T[] newarray = new T[capacity];
            if (_size > 0)
            {
                if (_head < _tail) {
                    Array.Copy(_array, _head, newarray, 0, _size);
                }else{
                    Array.Copy(_array, _head, newarray, 0, _array.Length - _head);
                    Array.Copy(_array, 0, newarray, _array.Length - _head, _tail);
                }
            }

            _array = newarray;
            _head = 0;
            _tail = (_size == capacity) ? 0 : _size;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            MyQueue<int> mq = new MyQueue<int>();
            mq.Enqueue(1);
            mq.Enqueue(2);
            mq.Enqueue(3);
            mq.Enqueue(4);

            Console.ReadKey(true);
        }
    }