<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:

    def longestConsecutive(self, nums: List[int]) -> int:
        nums_set = set(nums)
        nums_set_iter = nums_set.copy()
        result=0
        for num in nums_set_iter:
            if(num not in nums_set):
                continue
            next_num = num+1
            prev_num = num-1
            length_seq_temp = 1
            while(next_num in nums_set):
                length_seq_temp+=1
                nums_set.remove(next_num)
                next_num+=1
            while(prev_num in nums_set):
                length_seq_temp+=1
                nums_set.remove(prev_num)
                prev_num-=1
            if(result < length_seq_temp):
                result=length_seq_temp
        return result
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