C#实现简单优先队列

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using System;using System.Collections.Generic;namespace fofo.DataStructor{    public class PriorityQueue<T> where T: IComparable//, new()    {        private const int DEFAULT_CAP = 100;        private T[] _datas = null;        private int _capacity = DEFAULT_CAP;        private int _size = 0;        public PriorityQueue()            : this(DEFAULT_CAP)        {        }        public PriorityQueue(int capacity)        {            _capacity = capacity;            _datas = new T[_capacity];        }                public PriorityQueue(T[] initData)        {            if (_capacity <= initData.Length * 2)            {                _capacity = initData.Length * 2;            }            _datas = new T[_capacity];            Array.Copy(initData, 0, _datas, 1, initData.Length);            for (int i = initData.Length/2; i > 0; i--)            {                T item = _datas[i];                if (_datas[i * 2].CompareTo(_datas[i * 2 + 1]) < 0)                {                    _datas[i] = _datas[i * 2];                    _datas[i * 2] = item;                }                else                {                    _datas[i] = _datas[i * 2 + 1];                    _datas[i * 2] = item;                }                            }            _size = initData.Length;        }        public bool IsEmpty()        {            return _size == 0;        }        public void Enqueue(T item)        {            if (IsFull())            {                ReBuild();            }            int i;            for (i = ++_size; i > 1 && item.CompareTo(_datas[i / 2]) < 0; i /= 2)            {                _datas[i] = _datas[i / 2];            }            _datas[i] = item;        }        public T Dequeue()        {            if (IsEmpty())            {                throw new Exception("no item");            }            T first = _datas[1];            T last = _datas[_size--];            int i, child = 1;            for (i = 1; i * 2 <= _size; i = child)            {                child = i * 2;                if ((child != _size) && (_datas[child].CompareTo(_datas[child + 1]) > 0))                {                    child++;                }                if (last.CompareTo(_datas[child]) > 0)                {                    _datas[i] = _datas[child];                }                else                {                    break;                }            }            _datas[i] = last;                        return first;        }        public void Clear()        {            _datas = new T[_capacity];        }        private bool IsFull()        {            return _size == (_datas.Length - 1);        }               private void ReBuild()        {            _capacity = _capacity * 2;            T[] data = new T[_capacity];            Array.Copy(_datas, data, _datas.Length);            _datas = data;        }    }}