<p>Given an unsorted array of integers <code>nums</code>, return <em>the length of the longest consecutive elements sequence.</em></p>

<p>You must write an algorithm that runs in&nbsp;<code>O(n)</code>&nbsp;time.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [100,4,200,1,3,2]
<strong>Output:</strong> 4
<strong>Explanation:</strong> The longest consecutive elements sequence is <code>[1, 2, 3, 4]</code>. Therefore its length is 4.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [0,3,7,2,5,8,4,6,0,1]
<strong>Output:</strong> 9
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>0 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>9</sup> &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
</ul>

class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        cin.tie(nullptr);
        cout.tie(nullptr);
        ios::sync_with_stdio(false);

        std::unordered_map<int, int> s;
        s.reserve(nums.size());
        int maxi = 0;
        
        for(int i=0; i<nums.size(); i++){
            auto num = nums[i];
            if(s.find(num) != s.end())
                continue;

            auto left_it = s.find(num-1);
            auto right_it = s.find(num+1);
            
            auto left_move = left_it != s.end() ? left_it->second : 0;
            auto right_move = right_it != s.end() ? right_it->second : 0;

            s[num - left_move] = left_move + right_move + 1;
            s[num + right_move] = left_move + right_move + 1;
            s[num] = left_move + right_move + 1;
            
            maxi = max(maxi, left_move + right_move + 1);
        }

        return maxi;

        // std::unordered_map<int, bool> s;
        // s.reserve(nums.size());
        // for(const auto &it: nums){
        //     s[it] = false;
        // }
        // int sol = 0;
        // for(int i=0; i<nums.size(); i++){
        //     if(!s[nums[i]]){
        //         int cnt = nums[i];
        //         while(s.find(cnt-1) != s.end()){
        //             cnt--;
        //         }
        //         int current_sol=1;
        //         s[cnt]=true;
        //         while(s.find(cnt+1) != s.end()){
        //             current_sol++;
        //             cnt++;
        //             s[cnt]=true;
        //         }
        //         sol = max(sol, current_sol);
        //     }
        // }
        // return sol;
    }
};
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