斐波那契数列迭代和递归对比

斐波那契数列迭代方法和递归算法对比

1.递归算法

  int recursion(int n)
        {
            if (n < 2)
                return n;
            else
            {
                return recursion(n - 1) + recursion(n - 2);
            }
        }

2.递归算法（静态方法）

  static int recursionS(int n)
        {
            if (n < 2)
                return n;
            else
            {
                return recursionS(n - 1) + recursionS(n - 2);
            }
        }

3.迭代算法

 int Iteration(int n)
        {
            int a1, a2, a3;
            if (n < 2)
                return n;
            a1 = a2 = a3 = 1;
            while (n > 2)
            {
                n--;
                a3 = a1 + a2;
                a1 = a2;
                a2 = a3;

            }
            return a3;
        }

4.调用

            Stopwatch sw1 = new Stopwatch();
            sw1.Start();
            int i = Iteration(40);
            sw1.Stop();
            Response.Write(string.Format("{1}迭代時間：{0}<br/>", sw1.Elapsed, i));
            Stopwatch sw = new Stopwatch();
            sw.Start();
            int r=  recursion(40);
            sw.Stop();
            Response.Write(string.Format("{1}遞歸時間：{0}", sw.Elapsed, r));
            Response.Write("<br/>");
            Stopwatch sw2 = new Stopwatch();
            sw2.Start();
            int r1 = recursionS(40);
            sw2.Stop();
            Response.Write(string.Format("{1}遞歸時間(靜態)：{0}", sw2.Elapsed, r1));
            Response.Write("<br/>");

5.结果

102334155迭代時間：00:00:00.0001703
102334155遞歸時間：00:00:06.5017408
102334155遞歸時間(靜態)：00:00:06.2556308