C#堆栈

using System;

namespace ZH.DataFrame.AbstractData
{
    ObjectStackADT object堆栈#region ObjectStackADT object堆栈
    /**//// <summary>
    /// object堆栈(先进后出)
    /// </summary>
    public class StackADT
    {
        private object[] s;
        private int N;
        public StackADT(int maxN)
        {
            s=new object[maxN];N=0;
        }
        public bool isEmpty()
        {
            return (N==0);
        }
        /**//// <summary>
        /// 推入
        /// </summary>
        /// <param name="item"></param>
        public void push(object item)
        {
            s[N++]=item;
        }
        /**//// <summary>
        /// 推出
        /// </summary>
        /// <returns></returns>
        public object pop()
        {
            object t=s[--N];
            s[N]=null;
            return t;
        }

    }
    #endregion

    NodeStack(int) 链表int堆栈#region NodeStack(int) 链表int堆栈
/**//// <summary>
/// 链表int堆栈
/// </summary>
    public class NodeStack
    {
       
        private  class Node
        {
            public int item;public Node next;
            public Node(int item1,Node next)
            {
                item=item1;this.next=next;
            }
        }
        private Node head;
        public NodeStack()
        {
            head=null;
        }
        public bool isEmpty()
        {
           return (head==null);
        }
        public void push(int item)
        {
            head=new Node(item,head);
        }
        public int pop()