class Program
    {
        static void Main(string[] args)
        {
            int[] a = new int[] { 3, 12, 24, 36, 55, 68, 75, 88 };
            Program p = new Program();
            //调用方法(数组a,查找75,起始下标0,结束下标为数组最后值的下标)
            int b = p.Binsearch(a, 75, 0, a.Length - 1);
        }

        /// <summary>
        ///
        /// </summary>
        /// <param name="a">待查找数组,需有序排列,升降都可</param>
        /// <param name="key">待查找的值</param>
        /// <param name="low">数组起始下标</param>
        /// <param name="high">数组结束下标</param>
        /// <returns>待查找值的索引</returns>
        public int Binsearch(int[] a, int key, int low, int high)
        {
            if (low > high || high < 0)
            {
                return -1;
            }

            int mid = (low + high) / 2;

            if (key < a[mid])
            {
                return Binsearch(a, key, low, mid - 1);
            }
            else if (key > a[mid])
            {
                return Binsearch(a, key, mid + 1, high);
            }
            else
            {
                return mid;
            }

        }
    }
求版主讲解下递归思路

我只要是不会控制出口。每次都是死循环。 感谢版主。。