<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) {
        vector<int> ans;
        int t=nums.size();
        if(t<2) return t;
        sort(nums.begin(),nums.end());
        int start=nums[0];
        int maxi=-1;
        ans.push_back(start);
        for(int i=1;i<t;i++){
            if(nums[i-1]==nums[i]) continue;
            start++;
            if(nums[i]==(start)){
                ans.push_back(nums[i]);
            }
            else{
                cout<<i<<' ';
                int l=ans.size();
                maxi=max(maxi,l);
                start=nums[i];
                ans.clear();
                ans.push_back(start);
            }
        }
        int l=ans.size();
        maxi=max(maxi,l);
        //for(auto num:ans) cout<<num<<' ';
        return maxi;
    }
};
38686