<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) {
        int n = nums.size();
        sort(nums.begin(),nums.end());

        map<int,vector<pair<int,int>>>m;

        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                int x = nums[i]+nums[j];
                m[x].push_back(make_pair(i,j));
            }
        }
        vector<vector<int>>ans(1,vector<int>(4,0));
        map<vector<int>,int>rep;
        if(nums[0]>=0 && target<0){goto end;}

        for(int i=0;i<n;i++){
            for(int j=i+3;j<n;j++){
               if(j>i+3 && nums[j]==nums[i])i++; 
               long long int req = target;req-=nums[i];req-=nums[j];
               for(pair p:m[req]) {
                if(p.first>i && p.second<j){
                    vector<int>v = {nums[i],nums[p.first],nums[p.second],nums[j]};

                    long long sum = 0; for(int i:v)sum+=i;
                    if(sum!=target)continue;

                    if(rep[v]!=1){ans.push_back(v);rep[v]=1;}
                }
               }
               
            }
            
        }
        end:
        ans.erase(ans.begin());
        

        return ans;
              
    }
};
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