<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) {
        ios_base::sync_with_stdio(false);
std::cin.tie(NULL);
        if(nums.size()<=1){
            return nums.size();
        }
        sort(nums.begin(),nums.end());
        int maxlen=0;
        int cnt=0;
        for(int i=0;i<nums.size()-1;i++){
            if(nums[i]+1==nums[i+1]){
                cnt++;
                // continue;
            }
            if(nums[i]==nums[i+1]){
                if(i+2!=nums.size()){continue;}
                
            }
            if(nums[i]+1!=nums[i+1]||i+1==nums.size()-1){
                maxlen=max(cnt,maxlen);
                cnt=0;
            }
            
        }
        return maxlen+1;
    }
};
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