<p>Given a collection of numbers, <code>nums</code>,&nbsp;that might contain duplicates, return <em>all possible unique permutations <strong>in any order</strong>.</em></p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,1,2]
<strong>Output:</strong>
[[1,1,2],
 [1,2,1],
 [2,1,1]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,3]
<strong>Output:</strong> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 8</code></li>
	<li><code>-10 &lt;= nums[i] &lt;= 10</code></li>
</ul>

class Solution {
    private:
    void solve(vector<int> ip, vector<int> op, vector<vector<int>>& ans){
        if(ip.size() == 0){
            ans.push_back(op);
            return;
        }
        unordered_set<int> mp;
        for(int i=0; i<ip.size(); i++){
            if(mp.find(ip[i]) == mp.end()){
                mp.insert(ip[i]);

                vector<int> newip;
                for(int j=0; j<ip.size(); j++){
                    if(j != i) newip.push_back(ip[j]);
                }

                vector<int> newop = op;
                newop.push_back(ip[i]);

                solve(newip, newop, ans);
            }
        }

        return ;
    }
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>> ans;
        solve(nums, {}, ans);

        return ans;
    }
};
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