<p>Given an array <code>nums</code> of <code>n</code> integers, return <em>an array of all the <strong>unique</strong> quadruplets</em> <code>[nums[a], nums[b], nums[c], nums[d]]</code> such that:</p>

<ul>
	<li><code>0 &lt;= a, b, c, d&nbsp;&lt; n</code></li>
	<li><code>a</code>, <code>b</code>, <code>c</code>, and <code>d</code> are <strong>distinct</strong>.</li>
	<li><code>nums[a] + nums[b] + nums[c] + nums[d] == target</code></li>
</ul>

<p>You may return the answer in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,0,-1,0,-2,2], target = 0
<strong>Output:</strong> [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [2,2,2,2,2], target = 8
<strong>Output:</strong> [[2,2,2,2]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 200</code></li>
	<li><code>-10<sup>9</sup> &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
	<li><code>-10<sup>9</sup> &lt;= target &lt;= 10<sup>9</sup></code></li>
</ul>

class Solution {
public:
    vector<vector<int>> fourSum(vector<int>& nums, int target) {
	sort(nums.begin(), nums.end());
	
	unordered_map<int, int> m;
	

	
	
	vector<vector<int>> output;
	
	set<vector<int>> exists;
	
	
	for (int i = 0; i < nums.size(); i++)
	{
		m[nums[i]] = i;
	}
	
	for (int i = 0; i < nums.size(); i++)
	for (int j  = i+1; j < nums.size(); j++)
	for (int k = j+1; k < nums.size(); k++)
	{
		long rest = (long) target -(long) nums[i] -(long) nums[j] -(long) nums[k];
		if ((rest > INT_MAX) || (rest < INT_MIN))
			continue;
		vector<int> to_insert = {nums[i], nums[j], nums[k],(int) rest};
		
		
		if (m.contains(rest) && (m[rest] > k) && !exists.contains(to_insert))
		{
			exists.insert(to_insert);
			output.push_back(to_insert);
		}
	}
	return output;
    }
};
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