<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 {
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>> ans;

        if(nums.size() == 1){
            vector<int> t;
            t.push_back(nums[0]);
            ans.push_back(t);
            return ans;
        }

        unordered_set<int> s;

        for(int i=0;i<nums.size();i++){
            if(s.find(nums[i]) == s.end()){
                int n = nums[i];
                s.insert(n);
                vector<int> rm;

                for(int j=0;j<nums.size();j++){
                    if(i != j){
                        rm.push_back(nums[j]);
                    }
                }

                vector<vector<int>> p = permuteUnique(rm);

                for(vector<int> k:p){
                    k.insert(k.begin(), n);
                    ans.push_back(k);
                }
            }
            
        }

        return ans;
    }
};
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