斐波那契函数列

        static void Main(string[] args)
        {

            int a = fib(7);
             Console.Write(a);
            Console.ReadKey();
        }


        /// <summary>
        /// 非递归
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        public static int NoRecursionFib(int n)
        {
        
            int[] arr = new int[n-1];
            arr[0] = 1;
            arr[1]=1;
            if (n < 3)
            {
                return 1;

            }
            else
            {
                for (int i = 3; i < n; i++)
                {
                    arr[i] = (arr[i - 1] + arr[i - 2]);
                }            
            }
            return arr[n];              
        }



        /// <summary>
        /// 递归
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        public  static int fib(int n)
        {
            if (n <3)
            {
                return 1;
            }
            else
            {
                int a= fib(n - 1);
                int b= fib(n - 2);
                return a + b;

            }
        }