<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:
    void helper(vector<int>& nums, int i, vector<int>& results, set<vector<int>>& subset) {
        // Base case: if index reaches the end of the nums array
        if (i >= nums.size()) {
            subset.insert(results);  // Insert current subset into the set
            return;
        }

        // Exclude the current element
        helper(nums, i + 1, results, subset);

        // Include the current element
        results.push_back(nums[i]);
        helper(nums, i + 1, results, subset);
        results.pop_back();  // Backtrack to remove the last included element
    }

    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        vector<int> results;                // Temporary vector to store a subset
        set<vector<int>> subset;            // Set to store unique subsets

        sort(nums.begin(), nums.end());     // Sort to handle duplicates
        helper(nums, 0, results, subset);   // Start recursive helper function
        
        // Convert set to vector
        vector<vector<int>> result(subset.begin(), subset.end());
        return result;
    }
};

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