<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:
int n;
void call(vector<int> arr,vector<vector<int>> &ans,int idx){
    if(idx==n-1){
        ans.push_back(arr);
        return;
    }
    call(arr,ans,idx+1); 
    for(int i=idx+1;i<n;i++){
        if(arr[i]!=arr[idx]){
            swap(arr[i],arr[idx]);
            call(arr,ans,idx+1); 
            // swap(arr[i],arr[idx]);
        }
    }
}
    vector<vector<int>> permuteUnique(vector<int>& arr) {
       vector<vector<int>> ans;
       vector<int> temp;
       sort(arr.begin(),arr.end());
       n=arr.size();
       call(arr,ans,0); 
       return ans;
    }
};
// class Solution {
// public:
//     void recursion(vector<int> num, int i, int n, vector<vector<int> > &result) {
//         if(i == n-1){
//             result.push_back(num);
//             return;
//         }

//         for(int k = i; k < n; k++){
//             if(k != i && num[k] == num[i]) continue;

//             swap(num[k], num[i]);
//             recursion(num, i+1, n, result);
//         }
//     }
//     vector<vector<int> > permuteUnique(vector<int> &num) {
//         sort(num.begin(), num.end());

//         int n = num.size();

//         vector<vector<int>> result;
//         recursion(num, 0, n, result);
        
//         return result;
//     }
// };


13905