<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:
std::vector<int> deleteAtIndex(std::vector<int> vec, int index) {
	std::vector<int> res = {};
	res.resize(vec.size() - 1);

	int j = 0;

	for (int i = 0; i < vec.size(); i++) {
		if (i == index) continue;

		res[j] = vec[i];
		j++;
	}
	
	return res;
}
void permuteUniqueBacktracking(std::vector<std::vector<int>>& res, std::vector<int> nums, std::vector<int> backtrackingRes) {
	if (nums.size() <= 1) {
		backtrackingRes.push_back(nums[0]);
		res.push_back(backtrackingRes);
		return;
	}

	std::map<int, bool> checkUnique = {};

	backtrackingRes.resize(backtrackingRes.size() + 1);

	for (int i = 0; i < nums.size(); i++) {
		if (checkUnique[nums[i]]) continue;
	
		checkUnique[nums[i]] = 1;
		backtrackingRes[backtrackingRes.size() - 1] = nums[i];
		permuteUniqueBacktracking(res, deleteAtIndex(nums, i), backtrackingRes);
	}
}

std::vector<std::vector<int>> permuteUnique(std::vector<int>& nums) {
	std::vector<std::vector<int>> res = {};
	std::vector<int> backtrackingRes = {};

	permuteUniqueBacktracking(res, nums, backtrackingRes);

	return res;
}
};
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