gold-8-4

幂集。编写一种方法，返回某集合的所有子集。集合中不包含重复的元素。

说明：解集不能包含重复的子集。

示例:

 输入： nums = [1,2,3]
 输出：
[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public List<List<Integer>> subsets(int[] nums) {
        if (nums == null || nums.length == 0) {
            return new ArrayList<>();
        }

        List<List<Integer>> result = new ArrayList<>();
        getSubSets(result, nums, 0, new ArrayList<>());
        return result;
    }

    private void getSubSets(List<List<Integer>> result, int[] nums, int index, List<Integer> curRes) {
        if (index == nums.length) {
            List<Integer> one = new ArrayList<>(curRes);
            result.add(one);
            return;
        }

        curRes.add(nums[index]);
        getSubSets(result, nums, index + 1, curRes);
        curRes.remove(curRes.size() - 1);
        getSubSets(result, nums, index + 1, curRes);
    }
}
//leetcode submit region end(Prohibit modification and deletion)