Given a collection of numbers, return all possible permutations. For example, [1,2,3] have the following permutations: [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1]. 解题思路: 本题解题方法多多,为防止重复,决定使用Set的dfs算法,JVVA实现如下: static public List<List<Int…