题目: 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], [1,2,1], and [2,1,1]. 题解: 这道题跟Permutaitons没啥大的区别,就是结果去重. 我之前也有写过去重的两个方法: 一…