Subsets II.java

Given a collection of integers that might contain duplicates, S, 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 S = [1,2,2], a solution is:

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

public class Solution {
    public ArrayList<ArrayList<Integer>> subsetsWithDup(int[] num) {
        Arrays.sort(num);
        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
        ArrayList<Integer> path = new ArrayList<Integer>();
        subsets(num, 0, path, result);
        return result;
    }
    
    private void subsets(int[] num, int begin, ArrayList<Integer> path, ArrayList<ArrayList<Integer>> result) {
        result.add(new ArrayList<Integer>(path));
        for (int i = begin; i < num.length; i++) {
            if (i > begin && num[i - 1] == num[i]) {
                continue;
            }
            path.add(num[i]);
            subsets(num, i + 1, path, result);
            path.remove(path.size() - 1);
        }
    }
}