fibonacci数列算法求解的三种算法比较

using System;
using System.Diagnostics;

namespace myFib
{
    /**//// <summary>
    /// Fib 的摘要说明。
    /// fibonacci数列算法
    /// </summary>
    public class Fib
    {
        public Fib()
        {
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }

        static void Main(string[] args)
        {
            bool iscon=true;
            while(iscon)
            {
                System.Console.WriteLine("请输入一个整数或exit退出：");
                string strcon=System.Console.ReadLine();
                if (strcon.ToLower()=="exit")
                    iscon=false;
                else
                {
                    try
                    {
                        long myinput=long.Parse(strcon);

                        System.Console.WriteLine("请选择计算方法：1.迭代法 2.数组算法 3.递归算法");
                        int iway=int.Parse(System.Console.ReadLine());
                        long mResult=0;
                        StopWatch sw=new StopWatch();
                        sw.start();
                    
                        switch (iway)
                        {
                            case 1:
                                mResult=getcommon(myinput);
                                System.Console.WriteLine("迭代法的结果是：" + mResult.ToString());
                                System.Console.WriteLine("迭代法的执行时间是：" +sw.elapsed().ToString());
                                break;
                            case 2:
                                mResult=getArrayResult(myinput);
                                System.Console.WriteLine("数组算法的结果是：" + mResult.ToString());
                                System.Console.WriteLine("数组算法的执行时间是：" +sw.elapsed().ToString());
                                break;
                            case 3:
                                mResult=getResult(myinput);
                                System.Console.WriteLine("递归算法的结果是：" + mResult.ToString());
                                System.Console.WriteLine("递归算法的执行时间是：" +sw.elapsed().ToString());
                                break;
                            default:
                                System.Console.WriteLine("你什么都没选！");
                                break;
                        }
                        
                        
                    }
                    catch (System.Exception ex)
                    {
                       System.Console.WriteLine(ex.Message);
                    }
                }
                
            }
        }

        static Int64 getResult(Int64 n)
        {
            if (n<1)
                return 0;
            else if (n<3)
                return 1;
            else
                return  getResult(n-1)+ getResult(n-2);
            
        }

    
        static long getArrayResult(long n)
        {
            long[] test = new long[n];
            if (n<1)
                return 0;
            else
            {
                test[0] = 1;
                test[1] = 1;
                for(int i=2;i<n;i++)
                {
                    test[i] = test[i-1]+test[i-2];
                }
           
                return test[n-1];
            }
        }

        static long getcommon(long n)
        {

            if (n<1)
                return 0;
            else if (n<3)
                return 1;
            else
            {
                int a=1;
                int b=1;
                int s=0;
                for (int i=3;i<=n;i++)
                {
                    s=a+b;
                    a=b;
                    b=s;
                }
                return s;
            }
        }
    }

    class StopWatch 
    { 
        private int mintStart; 

        public void start() 
        { 
            mintStart =System.Environment.TickCount;
        } 

        public long elapsed() 
        { 
            return System.Environment.TickCount - mintStart;
        } 
    } 


}

//在本程序中,迭代法和数组算法的执行效率远远高于递归方法.所以此数列不一定要采用递归,用非递归的方法更有效率.如果输入45,就可以看到效果了,用递归就要等待很久.