算法－第四版－练习1.3.6解答

Stack<String> stack = new Stack<String>();
while (!q.isEmpty())
stack.push(q.dequeue());
while (!stack.isEmpty())
q.enqueue(stack.pop());

/**
* Description :
* Author      : mn@furzoom.com
* Date        : Sep 28, 2016 10:21:54 AM
* Copyright (c) 2013-2016, http://furzoom.com All Rights Reserved.
*/
package com.furzoom.lab.algs.ch103;

import java.util.Iterator;

import edu.princeton.cs.algs4.StdIn;

/**
* ClassName    : Queue <br>
* Function     : TODO ADD FUNCTION. <br>
* date         : Sep 28, 2016 10:21:54 AM <br>
*
* @version
*/
public class Queue<Item> implements Iterable<Item>
{
private Node first;
private Node last;
private int n;

private class Node
{
Item item;
Node next;
}

public boolean isEmpty()
{
return first == null;
}

public int size()
{
return n;
}

public void enqueue(Item item)
{
Node oldlast = last;
last = new Node();
last.item = item;
last.next = null;
if (isEmpty())
{
first = last;
}
else
{
oldlast.next = last;
}
n++;
}

public Item dequeue()
{
Item item = first.item;
first = first.next;
if (isEmpty())
{
last = null;
}
n--;
return item;
}

@Override
public Iterator<Item> iterator()
{
return new QueueIterator();
}

private class QueueIterator implements Iterator<Item>
{
private Node current = first;
@Override
public boolean hasNext()
{
return current != null;
}

@Override
public Item next()
{
Item item = current.item;
current = current.next;
return item;
}
}
}

/**
* Description :
* Author      : mn@furzoom.com
* Date        : Sep 28, 2016 4:20:38 PM
* Copyright (c) 2013-2016, http://furzoom.com All Rights Reserved.
*/
package com.furzoom.lab.algs.ch103;

/**
* ClassName    : E10306 <br>
* Function     : TODO ADD FUNCTION. <br>
* date         : Sep 28, 2016 4:20:38 PM <br>
*
* @version
*/
public class E10306
{
public static void test(Queue<String> q)
{
Stack<String> stack = new Stack<String>();
while (!q.isEmpty())
stack.push(q.dequeue());
while (!stack.isEmpty())
q.enqueue(stack.pop());
}

public static void main(String[] args)
{
Queue<String> q = new Queue<String>();
q.enqueue("a");
q.enqueue("b");
q.enqueue("c");
q.enqueue("d");

for (String s : q)
System.out.print(s + " ");
System.out.println();

test(q);

for (String s : q)
System.out.print(s + " ");
System.out.println();

}

}

a b c d
d c b a