<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:
    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
        nums.sort()
        res = []
        
        for i in range(len(nums)):
            if i > 0 and nums[i - 1] == nums[i]: # avoids duplicates
                continue
                          
            for j in range(i+1, len(nums)):
                if j > i+1 and nums[j - 1] == nums[j]: # avoids duplicates
                    continue
                l = j + 1
                r = len(nums) - 1
                
                while l < r:
                    fourSum = nums[i] + nums[j] + nums[l] + nums[r]
                    if fourSum < target:
                        l += 1
                    elif fourSum > target:
                        r -= 1
                    else:
                        res.append([nums[i], nums[j], nums[l], nums[r]])
                        l += 1
                        while nums[l] == nums[l-1] and l < r:
                            l += 1
        
        return res
16300