递归算法是把问题转化为规模缩小了的同类问题的子问题。然后递归调用函数（或过程）来表示问题的解。用递归来输出数组非常简单。-Recursive algorithm is to reduce the size of the problem into sub-problems of similar problems. Then recursively call the function (or process) to represent the solution of the problem. Use recursion to the output array is very simple.