class Solution {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        backtrack(result, new ArrayList<Integer>(), nums);
        return result;
    }
    
    public void backtrack(List<List<Integer>> result, List<Integer> temp, int [] nums)
    {
        if(temp.size() == nums.length)
            result.add(new ArrayList<>(temp));
        else
        {
            for(int i=0; i<nums.length; i++)
            {
                if(temp.contains(nums[i])) continue;
                temp.add(nums[i]);
                backtrack(result, temp, nums);
                temp.remove(temp.size()-1);
            }
        }
    }
}