[leedcode 141] Linked List Cycle
2001 ワード
Given a linked list, determine if it has a cycle in it.
Follow up:Can you solve it without using extra space?
Follow up:Can you solve it without using extra space?
/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public boolean hasCycle(ListNode head) {
// , , 1, , ,fast==null fast , false
if(head==null) return false;
ListNode fast=head;
ListNode slow=head;
while(fast!=null&&fast.next!=null){
fast=fast.next.next;
slow=slow.next;
if(fast==slow) return true;
}
return false;
}
}