參考資料

加上去重複的條件就是了沒注意一定要先sort一下

public class Solution {
    /*
     * @param nums: A set of numbers.
     * @return: A list of lists. All valid subsets.
     */
  public List<List<Integer>> subsetsWithDup(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        List<Integer> item = new
 
 ArrayList<>();
        if (nums == null) {
            return result;
        }
        if (nums.length == 0) {
            result.add(item);
            return result;
        }
        Arrays.sort(nums);
        for (int i = 0; i <= nums.length; i++) {
            item.clear();
            dfs(nums, 0
 
, i, item, result);
        }
        return result;

    }

    public void dfs(int[] nums, int step, int size, List<Integer> item, List<List<Integer>> result) {
        if (step == size) {
            result.add(new ArrayList<>(item));
            return;
        }
        for
 
 (int i = step; i < nums.length; i++) {
            if (i != step && nums[i] == nums[i - 1]) {
                continue;
            }
            item.add(nums[i]);
            dfs(nums, i + 1, size, item, result);
            item.remove(item.size() - 1);

        }
    }
}