use num set for time limit exceeded

Author: MJ Kang

longest-consecutive-sequence/mandoolala.py

@@ -4,13 +4,11 @@ class Solution:
     def longestConsecutive(self, nums: List[int]) -> int:
         num_set = set(nums)
         longest = 0
-
-        for num in nums:
-            if num - 1 not in num_set:
-                cnt = 1
-                next_num = num + 1
-                while next_num in num_set:
-                    cnt += 1
-                    next_num += 1
-                longest = max(longest, cnt)
+        for num in num_set:
+            if num - 1 in num_set:
+                continue
+            length = 1
+            while num + length in num_set:
+                length += 1
+            longest = max(length, longest)
         return longest