Algs4-1.3.48双向队列与栈

1.3.48双向队列与栈。用一个双向队列实现两个栈，保证每个栈操作只需要常数次的双向队列操作(请见练习1.3.33)。
答：

public class StackDouble<Item>
{
    private Deque<Item> q=new Deque<Item>();
    ///////////Stack of Left
    private int NLeft=0;
    public boolean isEmptyLeft()
    {return NLeft==0;}
   
    public int sizeLeft()
    {return NLeft;}
   
    public void pushLeft(Item item)
    {
        q.pushLeft(item);
        NLeft++;
    }
   
    public Item popLeft()
    {
       if (NLeft==0) return null;
        Item item=q.popLeft();
        NLeft--;
        return item;
    }
    ///////////Stack of Right
    private int NRight=0;
    public boolean isEmptyRight()
    {return NRight==0;}
   
    public int sizeRight()
    {return NRight;}
   
    public void pushRight(Item item)
    {
        q.pushRight(item);
        NRight++;
    }
   
    public Item popRight()
    {
        if(NRight==0) return null;
        Item item=q.popRight();
        NRight--;
        return item;
    }
   
    public static void main(String[] args)
    {
        StackDouble<String> s=new StackDouble<String>();
        s.pushLeft("1");
        s.pushLeft("2");
        s.pushLeft("3");
        //
        s.pushRight("4");
        s.pushRight("5");
        s.pushRight("6");
        StdOut.println("Stack of Left size is:"+s.sizeLeft());
        StdOut.println("Stack of Right size is:"+s.sizeRight());
        //
        StdOut.println("Stack of Left element is:");
        for(int i=0;i<7;i++)
            StdOut.print(s.popLeft()+" ");
        //
        StdOut.println();
        StdOut.println("Stack of Right element is:");
        for(int i=0;i<7;i++)
            StdOut.print(s.popRight()+ " ");
    }
}