<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, vector<vector<int>>& ans, int index){
        if(index >= nums.size()){
            for(int i = 0; i<ans.size(); i++){
                if(ans[i] == nums){
                    return ;
                }
            }
            ans.push_back(nums);
        }

        for(int i = index; i<nums.size(); i++){
            swap(nums[index], nums[i]);
            solve(nums, ans, index+1);
            swap(nums[index], nums[i]);
        }
    }
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>> ans;
        int index = 0;
        solve(nums, ans, index);

        return ans;
    }
};
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