<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:
    string convertString(vector<int>& vec){
        string res = "";
        for(int i: vec){
            res += to_string(i);
        }
        return res;
    }
    vector<vector<int>> twoPointer(vector<int>& nums, long target, int start){
        // how do u handle duplicate
        vector<vector<int>> result;
        int i = start, j = nums.size() - 1;
        while(i >= start && i < j && j <= nums.size() - 1){
            if(nums[i] + nums[j] == target){
                result.push_back({nums[i], nums[j]});
                i++;
            }
            if(nums[i] + nums[j] > target){
                j--;
            }
            if(nums[i] + nums[j] < target){
                i++;
            }
        }

        return result;
    }
    vector<vector<int>> fourSum(vector<int>& nums, int target) {
        unordered_set<string> uniqueVec;
        vector<vector<int>> result;
        sort(nums.begin(), nums.end());


        for(int i = 0; i < nums.size(); i++){
            for(int j = i + 1; j < nums.size(); j++){
                long sum = (nums[i] + nums[j]);
                long newTar = target - sum;
                vector<vector<int>> combinations = twoPointer(nums, newTar, j+1);
                for(int k = 0; k < combinations.size(); k++){
                    combinations[k].insert(combinations[k].begin(), {nums[i], nums[j]});
                    string key = convertString(combinations[k]);
                    if(uniqueVec.find(key) == uniqueVec.end()){
                        result.push_back(combinations[k]);
                        uniqueVec.insert(key);
                    }
                }
            }
        }




        return result;
    }
};
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