<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 helper(int idx,vector<int>&nums,vector<vector<int>>&ans){
    if(idx==nums.size()){
        ans.push_back(nums);
        return;
    }
    for(int i=idx;i<nums.size();i++){
        swap(nums[i],nums[idx]);
        helper(idx+1,nums,ans);
        swap(nums[i],nums[idx]);
    }
   }
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>>ans;
        helper(0,nums,ans);
        set<vector<int>>st;
        for(int i=0;i<ans.size();i++){
            st.insert(ans[i]);
        }
        vector<vector<int>>unique(st.begin(),st.end());
        return unique;
    }
};
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