1、Queue声明创建对象。(Queue为泛型对象。)
public class Queue<T> :IEnumerable<T>,System.Collections.ICollection,IReadOnlyCollection<T>
本质为Array对象存储数据。
Queue<string> qy = new Queue<string>();
private T[] _array
public Queue()
{
_array = Array.Empty<T>();
}
Queue<int> qy1 = new Queue<int>();
public Queue(int capacity)
{
if (capacity < )
throw new ArgumentOutOfRangeException(nameof(capacity), capacity, SR.ArgumentOutOfRange_NeedNonNegNum);
_array = new T[capacity];
}
Queue<int> qy2 = new Queue<int>(new List<int>()); public Queue(IEnumerable<T> collection)
{
if (collection == null)
throw new ArgumentNullException(nameof(collection)); _array = EnumerableHelpers.ToArray(collection, out _size);
if (_size != _array.Length) _tail = _size;
}
2、队列的空间是实际存储值的两倍，如果小于两倍则每次增场4的长度。
if (_size == _array.Length)
{
int newcapacity = (int)((long)_array.Length * (long)GrowFactor / );
if (newcapacity < _array.Length + MinimumGrow)
{
newcapacity = _array.Length + MinimumGrow;
}
SetCapacity(newcapacity);
}
3、Queue为先进先出。
进队列在数组末尾赋值
public void Enqueue(T item)
{
if (_size == _array.Length)
{
int newcapacity = (int)((long)_array.Length * (long)GrowFactor / );
if (newcapacity < _array.Length + MinimumGrow)
{
newcapacity = _array.Length + MinimumGrow;
}
SetCapacity(newcapacity);
} _array[_tail] = item;
MoveNext(ref _tail);
_size++;
_version++;
}
出队列则从头部取值
public T Dequeue()
{
int head = _head;
T[] array = _array; if (_size == )
{
ThrowForEmptyQueue();
} T removed = array[head];
if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
{
array[head] = default!;
}
MoveNext(ref _head);
_size--;
_version++;
return removed;
}
4、TryDequeue 与 Dequeue()区别在于 TryDequeue 判断size为0时，返回false 并out 泛型的默认值
public bool TryDequeue([MaybeNullWhen(false)] out T result)
{
int head = _head;
T[] array = _array; if (_size == )
{
result = default!;
return false;
} result = array[head];
if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
{
array[head] = default!;
}
MoveNext(ref _head);
_size--;
_version++;
return true;
}
注：MaybeNullWhenAttribute(Boolean) 返回值条件。 如果方法返回此值，则关联的参数可能为 null
5、Peek 仅仅时查看一下下一个要返回的值，不从数组移除
if (_size == )
{
result = default!;
return false;
} result = _array[_head];
return true;
随是拙见，但为原创，转载注明出处，敬谢
Queue 常用的方法大约就这些。先写道这里，碎觉。
以下为公众号，一起学起来~