<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:
    vector<vector<int>> result;
    void generate(vector<int> original, vector<int> ar, vector<bool> used) {

        if (ar.size() == original.size()) {
            result.push_back(ar);
            return;
        }

        for (int i = 0; i < original.size(); i++) {
            if (used[i]) {
                continue;
            }
            if (i > 0 && original[i] == original[i - 1] && !used[i - 1]) {
                continue;
            }
            ar.push_back(original[i]);
            used[i] = true;
            generate(original, ar, used);
            ar.pop_back();
            used[i] = false;
        }
    }
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        vector<int> ar;
        vector<bool> used(nums.size(), false);
        generate(nums, ar, used);
        return result;
    }
};

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