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

int len = nums.length;

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

if (len == 0) {

return res;

}

Arrays.sort(nums);

boolean[] used = new boolean[len];

Deque<Integer> path = new ArrayDeque<>(len);

dfs(nums, len, 0, used, path, res);

return res;

}

private void dfs(int[] nums, int len, int depth, boolean[] used, Deque<Integer> path, List<List<Integer>> res) {

if (depth == len) {

res.add(new ArrayList<>(path));

return;

}

for (int i = 0; i < len; i++) {

if (used[i]) {

continue;

}

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

continue;

}

path.addLast(nums[i]);

used[i] = true;

dfs(nums, len, depth + 1, used, path, res);

used[i] = false;

path.removeLast();

}

}

public static void main(String[] args) {

PermuteUnique permuteUnique = new PermuteUnique();

int[] nums = {1,1,2};

List<List<Integer>> res = permuteUnique.permuteUnique(nums);

System.out.println(res);

}