<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 solve(vector<vector<int>>& results, vector<int>& nums, vector<int>& subset, int idx) {
        // base case
        if (idx == nums.size())
            return;
        subset.push_back(nums[idx]);
        results.push_back(subset);
        solve(results, nums, subset, idx + 1);
        subset.pop_back();
        auto it = lower_bound(nums.begin(), nums.end(), nums[idx] + 1);
        if (it != nums.end()) {
            solve(results, nums, subset, it - nums.begin());
        }
    }

    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        vector<vector<int>> results;
        vector<int> subset;
        // sort nums
        sort(nums.begin(), nums.end());
        results.push_back(vector<int> ());
        solve(results, nums, subset, 0);
        return results;
    }
};
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