<p>Given an integer array <code>nums</code> that may contain duplicates, return <em>all possible</em> <span data-keyword="subset"><em>subsets</em></span><em> (the power set)</em>.</p>

<p>The solution set <strong>must not</strong> contain duplicate subsets. Return the solution in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> nums = [1,2,2]
<strong>Output:</strong> [[],[1],[1,2],[1,2,2],[2],[2,2]]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> nums = [0]
<strong>Output:</strong> [[],[0]]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10</code></li>
	<li><code>-10 &lt;= nums[i] &lt;= 10</code></li>
</ul>

class Solution {
public:

    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        unordered_set<string> existingSets;
        sort(nums.begin(), nums.end());
        vector<vector<int>> result;
        result.push_back({});
        run(existingSets, result, 0, nums, {}, "");
        return result;
    }


    void run(unordered_set<string>& existingSets, vector<vector<int>>& result, int pos, const vector<int>& nums, vector<int> currentSet, const string& currentHash)
    {
        if (pos >= nums.size())
        {
            return;
        }

        for(int i = pos; i < nums.size(); ++i)
        {
            vector<int> newList = currentSet;
            newList.push_back(nums[i]);
            const auto newHash = currentHash + std::to_string(nums[i]) + "_";
            if (!existingSets.contains(newHash))
            {
                existingSets.insert(newHash);
                result.push_back(newList);
                run(existingSets, result, i + 1, nums, newList, newHash);
            }
        }
    }
};
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