[LeetCode] Subsets II

Thought: easy DFS.

Code:
public class Solution {
    public static ArrayList<ArrayList<Integer>> result;
    public ArrayList<Integer> cache;
    public ArrayList<ArrayList<Integer>> subsetsWithDup(int[] num) {
        Arrays.sort(num);
        result = new ArrayList<ArrayList<Integer>>();
        cache = new ArrayList<Integer>();
        dfs(num, 0, num.length);
        return new ArrayList<ArrayList<Integer>>(new HashSet<ArrayList<Integer>>(result));
    }
    public void dfs(int[] num, int current, int length) {
        if (current == length) {
            result.add(new ArrayList<Integer>(cache));
            return;
        }
        dfs(num, current + 1, length);
        cache.add(num[current]);
        dfs(num, current + 1, length);
        cache.remove(cache.size() - 1);
    }
}