fix: add more

Author: gengjiawen

linked_list/_0141_linked_list_cycle.js

@@ -0,0 +1,53 @@
+// https://leetcode.com/problems/linked-list-cycle
+//
+// Given `head`, the head of a linked list, determine if the linked list has a cycle in it.
+//
+// There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the `next` pointer. Internally, `pos` is used to denote the index of the node that tail's `next` pointer is connected to. **Note that `pos` is not passed as a parameter**.
+//
+// Return `true` _if there is a cycle in the linked list_. Otherwise, return `false`.
+//
+// **Example 1:**
+//
+// ![](https://assets.leetcode.com/uploads/2018/12/07/circularlinkedlist.png)
+// ```
+// **Input:** head = [3,2,0,-4], pos = 1
+// **Output:** true
+// **Explanation:** There is a cycle in the linked list, where the tail connects to the 1st node (0-indexed).
+// ```
+//
+// **Example 2:**
+//
+// ![](https://assets.leetcode.com/uploads/2018/12/07/circularlinkedlist_test2.png)
+// ```
+// **Input:** head = [1,2], pos = 0
+// **Output:** true
+// **Explanation:** There is a cycle in the linked list, where the tail connects to the 0th node.
+// ```
+//
+// **Example 3:**
+//
+// ![](https://assets.leetcode.com/uploads/2018/12/07/circularlinkedlist_test3.png)
+// ```
+// **Input:** head = [1], pos = -1
+// **Output:** false
+// **Explanation:** There is no cycle in the linked list.
+// ```
+//
+// **Constraints:**
+//
+// *   The number of the nodes in the list is in the range `[0, 10<sup>4</sup>]`.
+// *   `-10<sup>5</sup> <= Node.val <= 10<sup>5</sup>`
+// *   `pos` is `-1` or a **valid index** in the linked-list.
+//
+// **Follow up:** Can you solve it using `O(1)` (i.e. constant) memory?
+
+export const hasCycle = function (head) {
+  let slow = head
+  let fast = head
+  while (fast && fast.next) {
+    slow = slow.next
+    fast = fast.next.next
+    if (slow === fast) return true
+  }
+  return false
+}