# 90. Subsets II (Medium)

https://leetcode.com/problems/subsets-ii/

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

```Input: [1,2,2]
Output:
[
[2],
[1],
[1,2,2],
[2,2],
[1,2],
[]
]
```

## Solutions

``````class Solution {
Set<String> strSet = new HashSet<>();

public List<List<Integer>> subsetsWithDup(int[] nums) {
Arrays.sort(nums);

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

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

combine(0, nums, track, ans);

return ans;
}

private void combine(int depth, int[] nums, List<Integer> track, List<List<Integer>> ans) {
if (depth == nums.length) {
if (!strSet.add(track.toString())) {
return;
}

List<Integer> sol = new ArrayList<>(track);

ans.add(sol);

return;
}

track.add(nums[depth]);
combine(depth + 1, nums, track, ans);
track.remove(track.size()-1);

combine(depth + 1, nums, track, ans);
}
}
``````

## References

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