使用数组实现栈和循环队列(JAVA语言）

这篇文章将讲述两个问题。一是如何使用数组实现一个栈，栈的大小可以伸缩。二是使用数组实现一个队列，为了充分的利用数组的空间，这里实现一个循环，构成循环队列。

（1）基于数组实现栈

package com.datastructure.stack;
import java.util.*;

public class MyStack {

	private Object[] array=null;
	private int capality;
	private final int defaultsize=10;
	private int size=0;
	private int top=-1;
	
	public MyStack()
	{
		this.capality=this.defaultsize;
		this.array=new Object[this.capality];
		this.size=0;
	}
	
	public MyStack(int capality)
	{
		this.capality=capality;
		this.array=new Object[capality];
		this.size=0;
	}
	
	public boolean isEmpty()
	{
		return size==0;
	}
	
	public int size()
	{
		return this.size;
	}
	
	public void push(T obj)
	{
		if(this.size stack=new MyStack();
		stack.push(1);
		stack.push(5);
		stack.push(2);
		stack.push(4);
		stack.push(3);
		while(!stack.isEmpty())
		{
			System.out.println(stack.pop());
		}
	}

}

运行结果如下所示：

3
4
2
5
1

（2）基于数组实现循环队列

package com.datastructure.stack;

public class MyQueue {
	
	private Object[] array=null;
	private int size;
	private int front;
	private int back;
	private boolean beginflag=true;
	private boolean endflag=false;
	
	public MyQueue(int size)
	{
		array=new Object[size];
		this.size=size;
		front=0;
		back=0;
	}
	
	public MyQueue()
	{
		this(10);
	}
	
	public void enqueue(Object obj)
	{
		if(isFull())
		{
			try {
				throw new Exception("队列已满！");
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		array[back]=obj;
		back=(back+1)%size;
	}
	
	public Object dequeue()
	{
		if(isEmpty())
			try {
				throw new Exception("队列为空！");
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		Object temp=array[front];
		array[front]=null;
		front=(front+1)%size;
		return temp;
	}
	
	public boolean isEmpty()
	{
		if(front==back)
		{
			if(!endflag)
			{
				endflag=true;
				return false;
			}
			return true;
		}
		else
			return false;
	}
	
	private boolean isFull()
	{
		if((back+1)%size==front)
		{
			if(beginflag)
				{beginflag=false;return false;}
			return true;
		}else
		{
			return false;
		}
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		MyQueue queue=new MyQueue(5);
		queue.enqueue(1);
		queue.enqueue(2);
		queue.enqueue(3);
		queue.enqueue(4);
		queue.enqueue(5);
		System.out.println(queue.dequeue());
		System.out.println(queue.dequeue());
		System.out.println(queue.dequeue());
		queue.enqueue(5);
		System.out.println(queue.dequeue());
		System.out.println(queue.dequeue());
		System.out.println(queue.dequeue());
		queue.enqueue(6);
		System.out.println(queue.dequeue());
	}

}

运行结果如下所示：

1
2
3
4
5
5
6