class Solution {
    public void backtrack(int n, List<Integer> temp, List<List<Integer>> res, int first){
        if(first == n)res.add(new ArrayList<Integer>(temp));
        for(int i=first;i<n;i++){
            Collections.swap(temp,i,first);
            if(!res.contains(temp))backtrack(n, temp, res, first+1);
            Collections.swap(temp,first,i);
        }
    }
    public List<List<Integer>> permuteUnique(int[] nums) {
        List<List<Integer>> res = new LinkedList<List<Integer>>();
        List<Integer> temp = new ArrayList<Integer>();
        for(int i:nums)
            temp.add(i);
        System.out.println(temp);
        backtrack(temp.size(), temp, res, 0);
        return res;
    }
}