解决思路

回溯算法

  public List<List<Integer>> subsets(int[] nums) {
        List<List<Integer>> res = new ArrayList<>();
        backtrack(0,nums,res,new ArrayDeque<>());
        return res;
    }
    private void backtrack(int begin,int[] nums,List<List<Integer>> res,Deque<Integer> tmp){
        res.add(new ArrayList<>(tmp));
        for (int j = begin;j < nums.length;j++){
            tmp.addLast(nums[j]);
            backtrack(j+1,nums,res,tmp);
            tmp.removeLast();
        }
    }