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0128-longest-consecutive-sequence/README.md

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+<h2><a href="https://leetcode.com/problems/longest-consecutive-sequence">128. Longest Consecutive Sequence</a></h2><h3>Medium</h3><hr><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>