Feat: 141. Linked List Cycle

Author: HC-kang

linked-list-cycle/HC-kang.ts

@@ -0,0 +1,42 @@
+class ListNode {
+  val: number;
+  next: ListNode | null;
+  constructor(val?: number, next?: ListNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.next = next === undefined ? null : next;
+  }
+}
+
+/**
+ * https://leetcode.com/problems/linked-list-cycle
+ * T.C. O(n)
+ * S.C. O(n)
+ */
+function hasCycle(head: ListNode | null): boolean {
+    const SET = new Set<ListNode>();
+    while (head) {
+        if (SET.has(head)) return true;
+        SET.add(head);
+        head = head.next
+    }
+    return false;
+};
+
+/**
+ * T.C. O(n)
+ * S.C. O(1)
+ */
+function hasCycle(head: ListNode | null): boolean {
+  let fast = head;
+  let slow = head;
+
+  while (fast && fast.next) {
+      fast = fast.next.next;
+      slow = slow!.next;
+
+      if (fast === slow) {
+          return true;
+      }
+  }
+  return false;
+};