<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>


auto fastIOSetup = []()noexcept{
    std::ios::sync_with_stdio(0);
    std::cin.tie(0);
    std::cout.tie(0);
    return 0;
}();

class Solution {
    std::unordered_set<int> data;
public:
    int longestConsecutive(vector<int>& nums) {
        std::ranges::sort(nums);
        int result = 0;
        int count = 0;
        auto last = std::numeric_limits<int>::max();
        for (auto x : nums) {
            if (x == last) continue;
            if (x - 1 == last) {
                ++count;
            } else {
                result = std::max(result, count);
                count = 1;
            }
            last = x;
        }
        return std::max(result, count);
    }
};
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