<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 swap(int &a,int &b)
    {
        int temp = a; 
        a = b;
        b = temp;
    }
    void solve(vector<vector<int>> &ans,vector<int> &a,int i,int j)
    {
        if(i>=a.size())
        {   
            ans.push_back(a);
            return ;
        }
        while(j<a.size())
        {      
            swap(a[i],a[j]);
            solve(ans,a,i+1,i+1);
            swap(a[i],a[j]);
            j++;
        }
    }
    
    vector<vector<int>> permuteUnique(vector<int>& a) {
        
        vector<vector<int>> ans;
        int i =0;
        solve(ans,a,i,i);
        sort(ans.begin(),ans.end());
        auto u = unique(ans.begin(),ans.end());
        ans.erase(u, ans.end());
        return ans;
    }
};
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