Linked List Cycle(Medium)
Given a linked list, determine if it has a cycle in it.
Follow up: Can you solve it without using extra space?
fast and slow pointer
public boolean hasCycle(ListNode head) {
if(head==null || head.next==null) return false;
ListNode fast=head,slow=head;
while(fast!=null&& fast.next!=null){
fast=fast.next.next;
slow=slow.next;
if(fast==slow) return true;
}
return false;
}