add longest-consecutive-sequence solution

Author: nakjun12

longest-consecutive-sequence/nakjun12.ts

@@ -0,0 +1,25 @@
+/*
+ * TC: O(n)
+ * SC: O(n)
+ * */
+function longestConsecutive(nums: number[]): number {
+  if (nums.length === 0) return 0;
+
+  const numSet = new Set(nums);
+  let longest = 0;
+
+  for (const num of nums) {
+    if (numSet.has(num - 1)) {
+      continue;
+    }
+
+    let length = 1;
+    while (numSet.has(num + length)) {
+      length++;
+    }
+
+    longest = Math.max(length, longest);
+  }
+
+  return longest;
+}