solve: longest consecutive sequence

Author: sounmind

longest-consecutive-sequence/sounmind.js

@@ -0,0 +1,30 @@
+from typing import List
+
+
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        # Time Complexity: O(n) where n is the length of nums
+        # Strategy: Use a set for O(1) lookups and only extend sequences from their starting points
+        if not nums:
+            return 0
+
+        max_streak = 0
+        num_set = set(nums)
+
+        # Only check sequences from their starting points to avoid redundant work
+        for num in num_set:
+            current_streak = 0
+
+            # Check if this number is the start of a sequence (no left neighbor)
+            if num - 1 not in num_set:
+                # Found a sequence start - extend it as far as possible
+                current_num = num
+
+                while current_num in num_set:
+                    current_streak += 1
+                    current_num += 1
+
+                # Update the longest streak found so far
+                max_streak = max(max_streak, current_streak)
+
+        return max_streak