class Solution:

    def permuteUnique(self, nums: List[int]) -> List[List[int]]:

        res = []

        if nums is None or len(nums) == 0:

            return res

        self.dfs(nums, 0, res)

        return res

    def dfs(self, nums, level, res):

        if level == len(nums):

            res.append(list(nums))

            return

        my_set = set()

        for i in range(level, len(nums)):

            if nums[i] not in my_set:

                my_set.add(nums[i])

                nums[i], nums[level] = nums[level], nums[i]

                self.dfs(nums, level + 1, res)

                nums[i], nums[level] = nums[level], nums[i]

class Solution {

    public List<List<Integer>> permuteUnique(int[] nums) {

        List<List<Integer>> arrList = new ArrayList<>();

        List<Integer> list = new ArrayList<>();

        boolean[] visited = new boolean[nums.length];

        Arrays.sort(nums);

        helper(arrList, list, visited, nums);

        return arrList;

    }

    private void helper(List<List<Integer>> arrList, List<Integer> list, boolean[] visited, int[] nums) {

        if (list.size() == nums.length) {

            arrList.add(new ArrayList<>(list));

            return;

        }

        for (int i = 0; i < nums.length; i++) {

            if (visited[i] || (i > 0 && nums[i] == nums[i - 1] && !visited[i - 1])) {

                continue;

            }

            visited[i] = true;

            list.add(nums[i]);

            helper(arrList, list, visited, nums);

            list.remove(list.size() - 1);

            visited[i] = false;

        }

    }

}