假设停在铁路调度站入口处的车厢序列的编号次序为1，2，3，…，n。设计一个程序，求出所有可能输出的长度为n的车厢序列。-Suppose stopped at the railway station at the entrance of the train scheduling sequence numbers in order of 1,2,3, ..., n. Design a program, find all possible output sequence of length n of the car.