<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>

#include <vector>
#include <set>
#include <algorithm> // For sorting
using namespace std;

class Solution {
public:
    void fn(int index, vector<int> current, vector<int>& nums, int n, set<vector<int>>& st) {
        if (index >= n) {
            st.insert(current); // Insert the current subset into the set
            return;
        }

        // Exclude the current element and recurse
        fn(index + 1, current, nums, n, st);

        // Include the current element and recurse
        current.push_back(nums[index]);
        fn(index + 1, current, nums, n, st);

        // No need to backtrack here, as 'current' is passed by value
    }

    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        vector<vector<int>> xd;
        vector<int> current;
        set<vector<int>> st;

        // Sort the array to handle duplicates
        sort(nums.begin(), nums.end());

        // Generate the subsets
        fn(0, current, nums, nums.size(), st);

        // Transfer the unique subsets from the set to the result vector
        for (const auto& subset : st) {
            xd.push_back(subset);
        }

        return xd;
    }
};

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