设集合R={r1,r2,...,rn}是要进行排列的n个元素，其中r1,r2,...,rn可能相同。

试着设计一个算法，列出R的所有不同排列。

即，给定n以及待排的n个可能重复的元素。计算输出n个元素的所有不同排列。-Set the set R = {r1, r2, ..., rn} n elements is to be arranged, wherein r1, r2, ..., rn may be the same.

Try to design an algorithm that lists all the different permutations of R.

That is, given n and n possible repeat of the elements to be ranked. Calculate the output of all different permutations of n elements.