Published Apr 03, 2022
[
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.
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).
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.
Input: head = [1], pos = -1
Output: false
Explanation: There is no cycle in the linked list.
[0, 10^4].-105 <= Node.val <= 105pos is -1 or a valid index in the linked-list./**
* Definition for singly-linked list.
* 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)
* }
* }
*/
function hasCycle(head: ListNode | null): boolean {
let slow: ListNode = head, fast: ListNode = head;
while(fast && fast.next){
slow = slow.next
fast = fast.next.next
if(slow === fast) {
return true;
}
}
return false;
};