Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note:
Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.
For example,
If nums = [1,2,2], a solution is:

[
[2],
[1],
[1,2,2],
[2,2],
[1,2],
[]
]

public class Solution {    public void helper(List<List<Integer>> res, List<Integer> item, int start, int[] nums, boolean[] isVisited) {        for(int i = start; i < nums.length; i ++) {            if(i > start && nums[i] == nums[i - 1])                continue;            if(!isVisited[i]) {                item.add(nums[i]);                isVisited[i] = true;                res.add(new ArrayList<Integer>(item));                helper(res, item, i + 1, nums, isVisited);                isVisited[i] = false;                item.remove(item.size() - 1);            }        }    }    //It can only can use the solution 1 of Subsets 1    public List<List<Integer>> subsetsWithDup(int[] nums) {        List<List<Integer>> res = new ArrayList<>();        if(nums == null || nums.length == 0)            return res;        Arrays.sort(nums);        res.add(new ArrayList<>());        helper(res, new ArrayList<Integer>(), 0, nums, new boolean[nums.length]);        return res;    }}