全排列

class  {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> list=new ArrayList<>();
        backTrack(list,new LinkedList<>(),nums);
        return list;
        
    }
    
    public void backTrack(List<List<Integer>> list,LinkedList <Integer> tempList,int [] nums)
    {
        if(tempList.size()==nums.length)
        {
            list.add(new ArrayList<>(tempList));
        }
        else
        {
            for(int i=0;i<nums.length;i++)
            {
                if(tempList.contains(nums[i])) continue;
                tempList.add(nums[i]);
                backTrack(list,tempList,nums);
                tempList.removeLast();
            }
        }
    }
}