LeetCode - Permutations II

public List<List<Integer>> permuteUnique(int[] nums) {
    //Arrays.sort(nums);
    boolean[] visited = new boolean[nums.length];
    List<Integer> cur = new LinkedList<>();
    Set<List<Integer>> result = new HashSet<>();
    helper(nums, visited, cur, result);
    List<List<Integer>> res = new LinkedList<>();
    res.addAll(result);
    return res;
}

private void helper(int[] nums, boolean[] visited, List<Integer> cur, Set<List<Integer>> result){
    if(cur.size() == nums.length){
        result.add(new LinkedList<>(cur));
        return;
    }
    for(int i = 0; i < nums.length; i++) {
        if(!visited[i]){
            visited[i] = true;
            cur.add(nums[i]);
            helper(nums, visited, cur, result);
            cur.remove(cur.size() - 1);
            visited[i] = false;
        }
    }
}