自定义堆栈（回文检测）

using System;
using System.Collections;

namespace CStack
{
    class Program
    {
        static void Main(string[] args)
        {
            CStack alist = new CStack();

            string ch;
            string word = "上海自来水来自海上";
            bool isPalindrome = true;

            for (int x = 0; x < word.Length; x++)
            {
                alist.Push(word.Substring(x,1));
            }

            int pos = 0;

            while (alist.Count > 0)
            {
                ch = alist.Pop().ToString();
                if (ch !=word.Substring(pos,1))
                {
                    isPalindrome = false;
                    break;
                }
                pos++;
            }


            Console.WriteLine(isPalindrome);
        }
    }

    public class CStack
    {
        private int p_index;
        private ArrayList list;

        public CStack()
        {
            list = new ArrayList();
            p_index = -1;
        }

        public int Count
        {
            get { return list.Count; }
        }

        public void Push(object item)
        {
            list.Add(item);
            p_index++;
        }

        public object Pop()
        {
            if (0 > p_index)
            {
                return null;
            }
            object obj = list[p_index];
            list.RemoveAt(p_index);
            p_index--;
            return obj;
        } 

        public void Clear()
        {
            list.Clear();
            p_index = -1;
        }

        public object Peek()
        {
            if (p_index < 0)
            {
                return null;
            }

            return list[p_index];
        }
    }
}