Add longest consecutive sequence

lc_0128_longest_consequtive.py

@@ -0,0 +1,38 @@
+"""128. Longest Consecutive Sequence
+
+Runtime: 334ms
+Beats 96.86% of users with Python3
+"""
+import unittest
+from itertools import count
+from typing import List
+
+
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        els = set(nums)
+
+        def gen():
+            for n in els:
+                if n - 1 not in els and n + 1 in els:
+                    for k in count(2):
+                        if n + k not in els:
+                            yield k
+                            break
+
+        return max(gen(), default=1) if nums else 0
+
+
+class LongestConsecutiveTests(unittest.TestCase):
+    def setUp(self):
+        self.sol = Solution()
+
+    def test_longestConsecutive(self):
+        self.assertEqual(self.sol.longestConsecutive([]), 0)
+        self.assertEqual(self.sol.longestConsecutive([100, 4, 200, 1, 3, 2]), 4)
+        self.assertEqual(self.sol.longestConsecutive([1, 2, 0, 1]), 3)
+        self.assertEqual(self.sol.longestConsecutive([0, 3, 7, 2, 5, 8, 4, 6, 0, 1]), 9)
+
+
+if __name__ == "__main__":
+    unittest.main()