已知如下一个递归程序，该程序的目的是输出给定字符的所有排列，请分析该程序的递归过程，然后将其用人工栈进行模拟，也就是将该递归程序转换成非递归程序：-Known as a recursive procedure, the objective of the program is all arranged output given character, please analyze the recursive process of the program, and then the artificial stack is simulated, also is the recursive procedure into non recursive program: