Given a linked list, determine if it has a cycle in it.<\/p>\n
To represent a cycle in the given linked list, we use an integer pos which represents the position (0-indexed) in the linked list where tail connects to. If pos is -1, then there is no cycle in the linked list.<\/p>\n
Example 1:<\/p>\n
Input: head = [3,2,0,-4], pos = 1
\nOutput: true
\nExplanation: There is a cycle in the linked list, where tail connects to the second node.<\/p>\n
Example 2:<\/p>\n
Input: head = [1,2], pos = 0
\nOutput: true
\nExplanation: There is a cycle in the linked list, where tail connects to the first node.<\/p>\n
Example 3:<\/p>\n
Input: head = [1], pos = -1
\nOutput: false
\nExplanation: There is no cycle in the linked list.<\/p>\n
Follow up:<\/p>\n
Can you solve it using O(1) (i.e. constant) memory?<\/p>\n
\r\n\r\n\/**\r\n * Definition for singly-linked list.\r\n * function ListNode(val) {\r\n * this.val = val;\r\n * this.next = null;\r\n * }\r\n *\/\r\n\r\n\/**\r\n * @param {ListNode} head\r\n * @return {boolean}\r\n *\/\r\nvar hasCycle = function(head) {\r\n \r\n if(head === null) return false;\r\n \r\n while(head.next !== null){\r\n if(head.val === 'checked') return true;\r\n head.val = 'checked';\r\n head = head.next;\r\n }\r\n \r\n return false;\r\n \r\n};\r\n\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"