C#アルゴリズム入門から走路第1章:リニアテーブルの両端キュー

デュアルエンドキュー
EnterFrontキューヘッダfront-OutFront削除キューヘッダエレメントfront++EnterRearキューヘッダrear削除キュー末尾rear++OutRear削除キュー末尾エレメントrear--

/// 

///       
/// 
///     
class CirDeque
{
    /// 

    ///       
    /// 
    private const int DEFAULT_SIZE = 10;
    /// 

    ///    
    /// 
    private T[] data;
    /// 

    ///    
    /// 
    private int front;
    /// 

    ///     
    /// 
    private int rear;
    /// 

    ///      
    /// 
    ///      
    public bool IsEmpty() => this.rear == this.front;
    /// 

    ///      
    /// 
    /// 
    public void Expand()
    {
        if((this.rear + 1) % this.data.Length == this.front)
        {
            Array.Resize(ref this.data, 
                this.data.Length + this.data.Length << 1);
        }
    }
    /// 

    ///    
    /// 
    ///   
    public CirDeque(int size=DEFAULT_SIZE)
    {
        this.data = new T[size];
        this.front = 0;
    }

    /// 

    ///     
    /// 
    ///     
    public void EnterFront(T val)
    {
        Expand();
        if(this.front==0)
        {
            this.front = this.data.Length - 1;
            this.data[this.front] = val;
        }
        else
        {
            this.front = (this.front - 1) % this.data.Length;
            this.data[this.front] = val;
        }
    }
    /// 

    ///     
    /// 
    ///     
    public void EnterRear(T val)
    {
        Expand();
        this.data[this.rear] = val;
        this.rear = (this.rear + 1) % this.data.Length;
    }
    /// 

    ///     
    /// 
    ///     
    public T OutFront()
    {
        if(IsEmpty())
            throw new IndexOutOfRangeException("  ");
        var val= this.data[this.front];
        this.front = (this.front + 1) % this.data.Length;
        return val;
    }
    /// 

    ///     
    /// 
    ///     
    public T OutRear()
    {
        if (IsEmpty())
            throw new IndexOutOfRangeException("  ");
        if(this.rear==0)
        {
            this.rear = this.data.Length - 1;
            return  this.data[this.rear];
        }
        else
        {
            this.rear = (this.rear - 1) % this.data.Length;
            return this.data[this.rear];
        }

    }
}