Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,2], a solution is:

[[2],[1],[1,2,2],[2,2],[1,2],[]
]

链接：  http://leetcode.com/problems/subsets-ii/

public class Solution {public List<List<Integer>> subsetsWithDup(int[] nums) {List<List<Integer>> res = new ArrayList<>();if(nums == null || nums.length == 0)return res;Arrays.sort(nums);ArrayList<Integer> list = new ArrayList<>();dfs(res, list, nums, 0);return res;}private void dfs(List<List<Integer>> res, ArrayList<Integer> list, int[] nums, int pos) {res.add(new ArrayList<Integer>(list));for(int i = pos; i < nums.length; i++) {if(i > pos && nums[i] == nums[i - 1])continue;list.add(nums[i]);dfs(res, list, nums, i + 1);list.remove(list.size() - 1);}}
}

public class Solution {public List<List<Integer>> subsetsWithDup(int[] nums) {List<List<Integer>> res = new ArrayList<>();if (nums == null || nums.length == 0) {return res;}Arrays.sort(nums);List<Integer> list = new ArrayList<>();subsetsWithDup(res, list, nums, 0);return res;}private void subsetsWithDup(List<List<Integer>> res, List<Integer> list, int[] nums, int pos) {res.add(new ArrayList<Integer>(list));for (int i = pos; i < nums.length; i++) {if (i > pos && nums[i] == nums[i - 1]) {continue;}list.add(nums[i]);subsetsWithDup(res, list, nums, i + 1);list.remove(list.size()- 1);}}
}

public class Solution {public List<List<Integer>> subsetsWithDup(int[] nums) {List<List<Integer>> res = new ArrayList<>();if (nums == null) return res;Arrays.sort(nums);getSubsetsWithDup(res, new ArrayList<Integer>(), nums, 0);return res;}private void getSubsetsWithDup(List<List<Integer>> res, List<Integer> list, int[] nums, int pos) {res.add(new ArrayList<>(list));for (int i = pos; i < nums.length; i++) {if (i > pos && nums[i] == nums[i - 1]) continue;list.add(nums[i]);getSubsetsWithDup(res, list, nums, i + 1);list.remove(list.size() - 1);}}
}