[leetcode]Linked List Cycle

Classic problem, use two pointers.

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public class Solution { public boolean hasCycle(ListNode head) { if (head == null) return false; ListNode fast = head.next == null?null:head.next.next; ListNode slow = head; while (fast != null){ if (slow == fast) return true; fast = fast.next == null?null:fast.next.next; slow = slow.next; } return false; } }