<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) {
        set<vector<int>> st;
        map<long long, int> M;
        for (auto it : nums) {
            M[it]++;
        }
        int n = nums.size();
        for (int i = 0; i < n; i++) {
            M[nums[i]]--;
            for (int j = i + 1; j < n; j++) {
                M[nums[j]]--;
                for (int k = j + 1; k < n; k++) {
                    M[nums[k]]--;
                    long long p=1;
                    long long req = target*p - (nums[i]*p + nums[j]*p + nums[k]*p )*p;
                    if(M[req]>0)
                    {
                        vector<int>temp = { nums[i],nums[j],nums[k],int(req) };
                        sort(temp.begin(),temp.end());
                        st.insert(temp);
                    }
                    M[nums[k]]++;
                }
                M[nums[j]]++;
            }
            M[nums[i]]++;
        }



        vector<vector<int>>ans(st.begin(),st.end());
        return ans;
    }
};
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