这是一个典型的非数值问题，如果使用非递归算法求解此问题，要设计复杂的算法，编写很长的程序。而使用递归算法可以使整个算法清晰，使程序简洁。本问题分析并建立递归算法的过程是典型的抽取问题本质、建立递归算法 并最终解决非数值问题递归实例。-This one a typical one number value issue, is it is it belong to algorithm ask and solve this question to pass to use, design the complicated algorithm , will write very long procedure . It can make the whole algorithm clear and use and pass and belong to the algorithm, make the procedure succinct . Case study this is it is it belong to course of algorithm typical extraction issue essence , is it pass algorithm of belonging to to set up to pass to set up And it is not a number value problem to solve finally and pass and belong to the instance