<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) {
        vector<vector<int>> result;
        unordered_map<long long, int> um_Hash;
        int vLen = (int)nums.size();
        // 순회를 해봅시다.
        for(int i = 0; i < vLen; ++i)
        {
            unordered_map<long long, int>::iterator it = um_Hash.find((long long)nums[i]);
            if(it == um_Hash.end())
            {
                um_Hash.insert({(long long)nums[i], 1});
            }else
            {
                ++it->second;
            }
        }

        for(int i = 0; i < vLen - 3; ++i)
        {
            for(int j = i + 1; j < vLen - 2; ++j)
            {
                for(int z = j + 1; z < vLen - 1; ++z)
                {
                    long long tmp = (long long)nums[i] + (long long)nums[j] + (long long)nums[z];
                    --um_Hash[nums[i]];
                    --um_Hash[nums[j]];
                    --um_Hash[nums[z]];

                    tmp = (long long)target - tmp;
                    unordered_map<long long, int>::iterator it = um_Hash.find(tmp);
                    if(it != um_Hash.end())
                    {
                        if(it->second != 0)
                        {
                            vector<int> newVec;
                            newVec.push_back(nums[i]);
                            newVec.push_back(nums[j]);
                            newVec.push_back(nums[z]);
                            newVec.push_back(tmp);
                            sort(newVec.begin(), newVec.end());

                            bool checker = false;
                            for(int x = 0; x < result.size(); ++x)
                            {
                                checker = true;
                                for(int y = 0; y < 4; ++y)
                                {
                                    if(result[x][y] != newVec[y])
                                    {
                                        checker = false;
                                    }
                                }

                                if(checker == true)
                                {
                                    break;
                                }
                            }
                            if(!checker)
                            {
                                result.push_back(newVec);
                            }                            
                        }
                    }

                    ++um_Hash[nums[i]];
                    ++um_Hash[nums[j]];
                    ++um_Hash[nums[z]];
                }
            }
        }

        return result;
    }
};
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