<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]]:
       n = len(nums) 
       answer = []
       nums.sort() 

       for i in range(n):
           if i > 0 and nums[i] == nums[i-1]:
              continue
           for j in range(i+1 , n):
             if j > i+1 and nums[j] == nums[j-1]:
                   continue
            
             lo, hi = j+1, n-1
             while lo < hi:
                summ = nums[i]+ nums[j]+nums[lo] +nums[hi]
                if summ == target :
                    answer.append([nums[i], nums[j], nums[lo], nums[hi]])
                    lo +=1
                    hi -=1
                    while lo <hi and nums[lo] == nums[lo - 1]:
                         lo +=1
                    while lo < hi and nums[hi] == nums[hi + 1]:
                         hi -= 1
                elif summ < target :
                     lo +=1
                else : 
                     hi -= 1
       return answer
16400