L141 Linked List Cycle
LinkedList
Problem
Given a linked list, determine if it has a cycle in it.
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.
是否有环
Solution
when slow == fast, there is a cycle;
public boolean hasCycle(ListNode head){
if(head == null || head.next == null) return false;
ListNode slow = head;
ListNode fast = head.next;
while(slow != fast){
if(fast == null || fast.next == null) return false;
slow = slow.next;
fast = fast.next.next;
}
return true;
}
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