<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:
void solve(vector<int>nums,int index,set<vector<int>>&v){
    if(index>=nums.size()){
        v.insert(nums);
        return;
    }
      unordered_set<int> used; 
    for(int i=index;i<nums.size();i++){
        if(used.find(nums[i])!=used.end()){
continue;
        }
        used.insert(nums[i]);
        swap(nums[index],nums[i]);
        solve(nums,index+1,v);
        swap(nums[index],nums[i]);
    }
}
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>>v;
       
        set<vector<int>>s;
         solve(nums,0,s);
        for(auto i:s){
            v.push_back(i);
        }
        return v;
    }
};
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