数据结构之栈

package org.stack.cn;

public interface StackADT {

	/***
	 * 向栈顶插入一个元素
	 * @param obj  插入的元素
	 */
	void push(Object obj);
	/**
	 * 栈顶删除一个元素
	 * @return
	 */
	Object pop();
	/**
	 * 返回栈顶元素的值
	 * @return
	 */
	Object peek();
	/***
	 * 判断是否为空栈 是-->true
	 * @return
	 */
	boolean isEmpty();
	/***
	 * 清楚栈中的元素成为空栈
	 */
	void clear();
}

package org.stack.cn;
/**
 * 栈的顺序存储结构操作实现
 * @author Administrator
 *
 */
public class SequenceSatck implements StackADT {

	private final int maxSize=10;
	private Object[] stackArray;
	private int top;//定义数组中所保存的栈顶元素的下标位置
	public SequenceSatck() {
		// TODO Auto-generated constructor stub
		top=-1;  //栈的初始位置为空
		stackArray=new Object[maxSize];   
	}
	public SequenceSatck(int n){
		if(n<=0){
			System.out.println("s数组长度要大于0");
		}
		top=-1;
		stackArray=new Object
;
	}
	@Override
	public void push(Object obj) {
		// TODO Auto-generated method stub
		if(top==stackArray.length-1){
			Object[] p=new Object[top*2+2];
			for(int i=0;i<top;i++){
				p[i]=stackArray[i];//复制数组内容到新数组中
				stackArray=p;
			}
		}
		top++;
		stackArray[top]=obj;
	}

	@Override
	public Object pop() {
		// TODO Auto-generated method stub
		if(top==-1){
			System.out.println("栈是空的");
			return null;
		}
		top--;
		return stackArray[top+1];
	}

	@Override
	public Object peek() {
		// TODO Auto-generated method stub
		if(top==-1){
			System.out.println("栈是空的，无法读取元素");
			return null;
		}
		return stackArray[top];
	}

	@Override
	public boolean isEmpty() {
		// TODO Auto-generated method stub
		return top==-1;
	}

	@Override
	public void clear() {
		// TODO Auto-generated method stub
		top=-1;
	}

}

package org.stack.cn;

/***
 * 栈的链式存储结构
 * @author Administrator
 *
 */
public class LinkStack implements StackADT {

	private Node top;   //定义top为栈顶指针的引用
	private class Node{
		private Object data;//数据域
		private Node next;  //指针域  存储下一个节点的引用
		public Node(Node next){
			this.next=next;
		}
		public Node(Object obj,Node next){
			this.data=obj;
			this.next=next;
		}
	}
	public LinkStack() {
		// TODO Auto-generated constructor stub
		top=null;
	}
	@Override
	public void push(Object obj) {
		// TODO Auto-generated method stub
		top=new Node(obj,top);
	}

	@Override
	public Object pop() {
		// TODO Auto-generated method stub
		if(top==null){
			System.out.println("栈是空的");
			return null;
		}
		Object x=top.data;
		top=top.next;
		return x;
	}

	@Override
	public Object peek() {
		// TODO Auto-generated method stub
		if(top==null){
			System.out.println("栈是空的");
			return null;
		}
		return top.data;
	}

	@Override
	public boolean isEmpty() {
		// TODO Auto-generated method stub
		return top==null;
	}

	@Override
	public void clear() {
		// TODO Auto-generated method stub
		top=null;
	}

}