<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:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        def swap(arr, i, j):
            arr[i], arr[j] = arr[j], arr[i]

        def p(arr,ans,ind):

            if len(arr)==ind:
                ans.append(arr.copy())
                return

            use=[0]*(21)

            for i in range(ind,len(arr)):
                if use[arr[i]+10]==0:
                    swap(arr, i, ind)
                    p(arr,ans,ind+1)
                    swap(arr, i, ind)
                    use[arr[i]+10]=1
        
        ans=[]
        
        p(nums,ans,0)
        

        return ans
        
16700