leetcode : subsetsII

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) {
        List<List<Integer>> result = new ArrayList<List<Integer>>();
        if(nums == null || nums.length == 0) {
            return result;
        }
        List<Integer> list = new ArrayList<Integer>();
        Arrays.sort(nums);
        backtrack(result, list, nums, 0);
        return result;
    }

    public void backtrack(List<List<Integer>> result, List<Integer> list, int[] nums, int position) {
        if(list.size() > nums.length) {
            return;
        }

        result.add(new ArrayList<Integer>(list));

        for(int i = position; i < nums.length; i++) {
            if(i > position && nums[i] == nums[i - 1]) {
                continue;
            }
            list.add(nums[i]);
            backtrack(result, list, nums, i + 1);
            list.remove(list.size() - 1);
        }
    }

}