题目描述 给出一组可能包含重复项的数字,返回该组数字的所有排列 例如: [1,1,2]的排列如下: [1,1,2],[1,2,1], [2,1,1]. Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2]have the following unique permutations: [1,1,2],[1,2…