class Solution {
    public List<List<Integer>> subsetsWithDup(int[] nums) {
    List<List<Integer>> ans = new ArrayList<>();
    Arrays.sort(nums); //排序
    getAns(nums, 0, new ArrayList<>(), ans);
    return ans;
}
  private void getAns(int[] nums, int start, ArrayList<Integer> temp, List<List<Integer>> ans) {
    ans.add(new ArrayList<>(temp));
    for (int i = start; i < nums.length; i++) {
        //和上个数字相等就跳过
        if (i > start && nums[i] == nums[i - 1]) {
            continue;
        }
        temp.add(nums[i]);
        getAns(nums, i + 1, temp, ans);
        temp.remove(temp.size() - 1);
    }
}
}