<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<vector<int>>& ans,vector<int>& nums,int i)
    {
        if(i>=nums.size())
        {
            ans.push_back(nums);
            return;
        }
        unordered_map<int,bool> visited;

        for(int j=i;j<nums.size();j++)
        {
            if(visited.find(nums[j])!=visited.end()) continue;
            else visited[nums[i]]=true;
           swap(nums[i],nums[j]);
           
           solve(ans,nums,i+1);
           swap(nums[i],nums[j]);
        }
    }
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        int i=0;
        vector<vector<int>> ans;
        solve(ans,nums,i);
        set<vector<int>>st;
        for(auto it:ans) st.insert(it);
        ans.clear();
        for(auto it:st) ans.push_back(it);
        return ans;
    }
};
37093