C# 斐波那契数列和1-200之间取100不重复的值

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DateTime start = DateTime.Now;

            int n = 5000;

            long arr = Foo(n, 0, 1);
            DateTime end = DateTime.Now;

            TimeSpan span = new TimeSpan(end.Ticks - start.Ticks);

            Console.WriteLine("第" + n + "位递归" + arr.ToString() + "费时:" + span.TotalSeconds.ToString());


            start = DateTime.Now;
            arr = Foo(n);
            end = DateTime.Now;

            span = new TimeSpan(end.Ticks - start.Ticks);

            Console.WriteLine("第" + n + "位循环" + arr.ToString() + "费时:" + span.TotalSeconds.ToString());


            Console.Read();
        }

        static int[] GetNumber()
        {
            int[] arr = new int[200];
            for (int i = 0; i < 200; i++)
            {
                arr[i] = i + 1;
            }

            for (int i = 0; i < 100; i++)
            {
                int n = (new Random()).Next(0, 199);
                int temp = arr[i];
                arr[i] = arr[n];
                arr[n] = temp;
            }

            int[] arr1 = new int[100];
            for (int i = 0; i < 100; i++)
            {
                arr1[i] = arr[i];
            }

            return arr1;
        }

        /// <summary>
        /// 递归方式
        /// </summary>
        /// <param name="n"></param>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        static long Foo(int n, long a, long b)
        {
            if (n == 1)
            {
                return b;
            }

            return Foo(n - 1, b, a + b);
        }

        /// <summary>
        /// 循环方式
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        static long Foo(int n)
        {
            long a = 1;
            long b = 1;
            long c = 1;

            for (int i = 3; i <= n; i++)
            {
                c = a + b;
                a = b;
                b = c;
            }
            return c;
        }


    }
}