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

// Note: 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],

// []

// ]

public class Solution {

public List<List<Integer>> subsetsWithDup(int[] nums) {

Arrays.sort(nums);

List<List<Integer>> result = new ArrayList<List<Integer>>();

if(nums.length == 0 || nums == null) return result;

helper(nums, new ArrayList<Integer>(), 0, result);

return result;

}

public void helper(int[] nums, ArrayList<Integer> current, int index, List<List<Integer>> result) {

result.add(current);

for(int i = index; i < nums.length; i++) {

if(i > index && nums[i] == nums[i - 1]) continue;

ArrayList<Integer> newCurrent = new ArrayList<Integer>(current);

newCurrent.add(nums[i]);

helper(nums, newCurrent, i + 1, result);

}

}

}