solve: longest consecutive sequence

Author: sounmind

longest-consecutive-sequence/evan.js

@@ -0,0 +1,38 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function (nums) {
+  const set = new Set(nums);
+  let longestStreak = 0;
+
+  for (const num of set) {
+    // Check if it's the start of a sequence
+    if (!set.has(num - 1)) {
+      let currentNum = num;
+      let currentStreak = 1;
+
+      // Find the length of the sequence
+      while (set.has(currentNum + 1)) {
+        currentNum += 1;
+        currentStreak += 1;
+      }
+
+      longestStreak = Math.max(longestStreak, currentStreak);
+    }
+  }
+
+  return longestStreak;
+};
+
+/**
+ * Time Complexity: O(n) where n is the length of the input array.
+ * Reason:
+ *   Creating the Set: O(n)
+ *   Iterating Through the Set: O(n)
+ *   Checking for the Start of a Sequence: O(n)
+ *   Finding the Length of the Sequence: O(n) across all sequences
+ *   Tracking the Longest Sequence: O(n)
+ *
+ * Space Complexity: O(n) because of the additional space used by the set.
+ */