[leetCode] Subsets II

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],
  []
]

public class Solution {
    List<List<Integer>> res = new ArrayList<List<Integer>>();

    public List<List<Integer>> subsetsWithDup(int[] nums) {
        Arrays.sort(nums);
        List<Integer> item = new ArrayList<Integer>();
        res.add(item);
        sub(nums, 0, item);
        return res;
    }

    private void sub(int[] nums, int index, List<Integer> input) {
        for (int i = index; i < nums.length; i++) {
            List<Integer> item = new ArrayList<Integer>(input);
            item.add(nums[i]);
            if (res.contains(item) == false) {
                res.add(item);
                sub(nums, i + 1, item);
            }
        }
    }
}