solve: 141. Linked List Cycle

Runtime: 53 ms, faster than 94.85% of JavaScript online submissions for Linked List Cycle.
Memory Usage: 52.7 MB, less than 80.49% of JavaScript online submissions for Linked List Cycle.

Author: sounmind

linked-list-cycle/evan.js

@@ -0,0 +1,27 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+
+/**
+ * @param {ListNode} head
+ * @return {boolean}
+ */
+var hasCycle = function (head) {
+  let fastPointer = head;
+  let slowPointer = head;
+
+  while (fastPointer !== null && slowPointer !== null) {
+    fastPointer = fastPointer?.next?.next;
+    slowPointer = slowPointer?.next;
+
+    if (fastPointer === slowPointer) {
+      return true;
+    }
+  }
+
+  return false;
+};