雙端佇列

雙端佇列是指允許兩端都可以進行入隊和出隊操作的佇列，其元素的邏輯結構仍是線性結構。將佇列的兩端分別稱為前端和後端，兩端都可以入隊和出隊。

• 定義佇列介面

package com.feifan;

/**
 * 佇列的基本方法
 * @author Donald
 * 2018-12-06 22:45:04 
 * @param <T>
 */
public interface DoubleQueInterface <T> {
    //佇列頭部增加元素
    public void addFrist(T newEntry);
    //佇列頭部移除元素
 

    public T removeFrist();
    //佇列尾部增加元素
    public void addLast(T newEntry);
    //佇列尾部移除元素
    public T removeLast();
    //佇列是否為空
    public boolean isEmpty();
    //佇列中元素的個數
    public int size();
    //清空佇列
    public void clear();
    //對列頭部遍歷佇列
    public void foreachFrist();
    //對列尾部遍歷佇列
    public void
 
 foreachLast();

}

• 佇列實現類

package com.feifan;

import java.io.Serializable;

public class DoubleQueueImpl<T> implements DoubleQueInterface<T> {
	
	//佇列的長度
	private int size;
	//隊首
	private NodeData headNode;
	//隊尾
	private NodeData tailNode;
	
	public DoubleQueueImpl() {
		this.size =
 
 0;
		this.headNode = null;
		this.tailNode = null;
	}

	//連結串列
	private class NodeData implements Serializable{
		private static final long serialVersionUID = 1L;
		//資料
		private T data;
		//頭節點
		private NodeData front;
		//尾節點
		private NodeData next;
		
		public NodeData(T data, DoubleQueueImpl<T>.NodeData front, DoubleQueueImpl<T>.NodeData next) {
			super();
			this.data = data;
			this.front = front;
			this.next = next;
		}
		public T getData() {
			return data;
		}
		public void setData(T data) {
			this.data = data;
		}
		public NodeData getFront() {
			return front;
		}
		public void setFront(NodeData front) {
			this.front = front;
		}
		public NodeData getNext() {
			return next;
		}
		public void setNext(NodeData next) {
			this.next = next;
		}
	}
	
	/**
	 * 隊頭增加元素
	 */
	@Override
	public void addFrist(T newEntry) {
		NodeData node= new NodeData(newEntry, null, headNode);
		if(isEmpty()) {
			tailNode=node;
		}else {
			headNode.setFront(node);
		}
		headNode=node;
		size++;
	}

	/**
	 * 移除頭元素
	 */
	@Override
	public T removeFrist() {
		T target=null;
		if(!isEmpty()) {
			target=headNode.getData();
			headNode=headNode.getNext();
			if(headNode==null) {
				tailNode=null;
			}
			size--;
		}
		return target;
	}

	/**
	 * 隊尾增加元素
	 */
	@Override
	public void addLast(T newEntry) {
		NodeData  nodeData = new NodeData(newEntry, tailNode, null);
		if(isEmpty()) {
			tailNode=nodeData;
		}else {
			tailNode.setNext(nodeData);
			tailNode=nodeData;
		}
		size++;
	}

	/**
	 * 移除隊尾元素
	 */
	@Override
	public T removeLast() {
		T target=null;
		if(!isEmpty()) {
			target=tailNode.getData();
			tailNode=tailNode.getFront();
			if(tailNode==null) {
				headNode=null;
			}
			size--;
		}
		return target;
	}

	/**
	 * 判斷佇列是否為空
	 */
	@Override
	public boolean isEmpty() {
		return size>0?false:true;
	}

	/**
	 * 佇列長度
	 */
	@Override
	public int size() {
		return size;
	}

	/**
	 * 清除佇列
	 */
	@Override
	public void clear() {
		headNode=null;
		tailNode=null;
		size=0;
	}

	/**
	 * 隊首迴圈遍歷佇列
	 */
	@Override
	public void foreachFrist() {
		if(isEmpty()) {
			throw new RuntimeException("當前佇列為空");
		}else {
			int temp=size;
			while(temp>0) {
				System.out.print(headNode.getData()+"\t");
				addLast(removeFrist());
				temp--;
			}
			System.out.println("======佇列正序遍歷完成======");
		}
	}

	/**
	 * 隊尾迴圈遍歷佇列
	 */
	@Override
	public void foreachLast() {
		if(isEmpty())
		{
			throw new RuntimeException("當前佇列為空");
		}else {
			int temp =size;
			while(temp>0)
			{
				System.out.print(tailNode.getData()+"\t");
				addFrist(removeLast());
				temp--;
			}
			System.out.println("======佇列倒序遍歷完成======");
		}
		
	}

}

測試方法

package com.feifan;

public class DoubleQueTest {
	public static void main(String[] args) {
		DoubleQueueImpl< Integer> duQue= new DoubleQueueImpl<>();
		duQue.addFrist(1);
		duQue.addFrist(2);
		duQue.addLast(3);
		duQue.addLast(4);
		System.out.println(duQue.size());
		duQue.foreachFrist();
		duQue.foreachLast();
		duQue.removeFrist();
		duQue.removeLast();
		System.out.println(duQue.size());
		duQue.foreachFrist();
		duQue.foreachLast();
		
	}

}

• 結果：
  

僅供參考

連結：https://pan.baidu.com/s/1eR7yWVv_ZdX-U4mKLo2Zrg
提取碼：a75w