Given a linked list, return the node where the cycle begins. If there is no cycle, return null.
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 ListNode detectCycle(ListNode head) {
if(head==null)return null;
ListNode slow=head;
ListNode fast=head;
do{
if(fast==null||fast.next==null)return null;
fast=fast.next.next;
slow=slow.next;
} while(fast!=slow);
slow=head;
while(slow.val!=Integer.MAX_VALUE){
//这样可以通过。。。投机？
slow.val=Integer.MAX_VALUE;
slow=slow.next;
}
return slow;
}
}