算法－第四版－练习1.3.32解答

问题

Steque。一个以栈为目标的队列（或称steque），是一种支持push、pop和enqueue操作的数据类型。为这种抽象数据类型定义一份API并给出一份基于链表的实现。

解决思路

/**
 * -----------------------------------------------------
 * public class Steque<Item> implements Iterable<Item>
 * -----------------------------------------------------
 *    boolean isEmpty()                
 *       void push(Item e)            添加一个元素到头部
 *       Item pop()                   从头部删除一个元素
 *       void enqueue(Item e)         添加一个元素到尾部
 * -----------------------------------------------------
 */

代码

/**
 * Description : 
 * Author      : mn@furzoom.com
 * Date        : Oct 26, 2016 1:47:35 PM
 * Copyright (c) 2013-2016, http://furzoom.com All Rights Reserved.
 */
/**
 * -----------------------------------------------------
 * public class Steque<Item> implements Iterable<Item>
 * -----------------------------------------------------
 *    boolean isEmpty()                
 *       void push(Item e)             添加一个元素到头部
 *       Item pop()                    从头部删除一个元素
 *       void enqueue(Item e)          添加一个元素到尾部
 * -----------------------------------------------------
 */
package com.furzoom.lab.algs.ch103;

import java.util.Iterator;

/**
 * ClassName    : Steque <br>
 * Function     : TODO ADD FUNCTION. <br>
 * date         : Oct 26, 2016 1:47:35 PM <br>
 * 
 * @version 
 */
public class Steque<Item> implements Iterable<Item>
{
    private Node first;
    private Node last;
    
    private class Node
    {
        public Item item;
        public Node next;
    }
    
    public boolean isEmpty()
    {
        return first == null;
    }
    
    public void enqueue(Item e)
    {
        Node node = new Node();
        node.item = e;
        node.next = null;
        if (isEmpty())
        {
            first = node;
            last = node;
        }
        else
        {
            last.next = node;
            last = node;
        }
    }
    
    public void push(Item e)
    {
        Node node = new Node();
        node.item = e;
        if (isEmpty())
        {
            first = node;
            last = node;
            node.next = null;
        }
        else
        {
            node.next = first;
            first = node;
        }
    }
    
    public Item pop()
    {
        if (isEmpty())
        {
            return null;
        }
        else
        {
            Item e = first.item;
            first = first.next;
            return e;
        }
    }
    
    @Override
    public Iterator<Item> iterator()
    {
        return new Iter();
    }
    
    private class Iter implements Iterator<Item>
    {
        private Node current = first;
        @Override
        public boolean hasNext()
        {
            return current != null;
        }
        
        @Override
        public Item next()
        {
            Item e = current.item;
            current = current.next;
            return e;
        }
    }
}

测试代码：

/**
 * Description : 
 * Author      : mn@furzoom.com
 * Date        : Oct 26, 2016 2:04:23 PM
 * Copyright (c) 2013-2016, http://furzoom.com All Rights Reserved.
 */
package com.furzoom.lab.algs.ch103;

import java.util.Iterator;

/**
 * ClassName    : E10332 <br>
 * Function     : TODO ADD FUNCTION. <br>
 * date         : Oct 26, 2016 2:04:23 PM <br>
 * 
 * @version 
 */
public class E10332
{
    public static void main(String[] args)
    {
        Steque<String> s = new Steque<String>();
        s.enqueue("d");
        s.enqueue("e");
        s.enqueue("f");
        s.push("c");
        s.push("b");
        s.push("a");
        System.out.println("Steque is:");
        Iterator<String> it = s.iterator();
        while (it.hasNext())
        {
            System.out.println(it.next());
        }
        
        System.out.println("pop up:");
        while (!s.isEmpty())
        {
            System.out.println(s.pop());
        }
    }
}

结果：

Steque is:
a
b
c
d
e
f
pop up:
a
b
c
d
e
f

算法－第四版－1.3 背包、队列和栈－习题索引汇总

算法－第四版习题索引汇总