[LeetCode Sync] Runtime - 43 ms (88.18%), Memory - 34.3 MB (29.62%)

Author: NinePiece2

Solutions/0128-longest-consecutive-sequence/README.md

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+<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><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [1,0,1,2]
+<strong>Output:</strong> 3
+</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>

Solutions/0128-longest-consecutive-sequence/solution.py

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+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        hash_table = set(nums)
+        result = 0
+
+        for num in hash_table:
+            if num - 1 not in hash_table:
+                val = num + 1
+                while val in hash_table:
+                    val += 1
+                result = max(result, val - num)
+
+        return result