feat: 128. Longest Consecutive Sequence

Author: gwbaik9717

longest-consecutive-sequence/gwbaik9717.js

@@ -0,0 +1,30 @@
+// Time complexity: O(n)
+// Space complexity: O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function (nums) {
+  let answer = 0;
+  const consecutiveDict = new Map();
+
+  for (const num of nums) {
+    consecutiveDict.set(num, true);
+  }
+
+  for (const num of nums) {
+    if (consecutiveDict.has(num - 1)) {
+      continue;
+    }
+
+    let length = 1;
+    while (consecutiveDict.has(num + length)) {
+      length++;
+    }
+
+    answer = Math.max(answer, length);
+  }
+
+  return answer;
+};