Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
Solution:
快慢指针追击问题。
/**
* 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)
{
if (head == null)
return false;
ListNode slow = head;
ListNode fast = head;
while(fast.next != null && fast.next.next != null)
{
slow = slow.next;
fast = fast.next.next;
if(slow == fast)
return true;
}
return false;
}
}
