check if thelinkedlist has a cycle exceptions threads arrays - reverse pattern matching

Question

Accepted Answer

To check if a linked list has a cycle, use Floyd's Tortoise and Hare algorithm.

Use two pointers, slow and fast, to traverse the linked list.
If there is a cycle, the fast pointer will eventually meet the slow pointer.
Example: 1->2->3->4->2 (cycle exists between 4 and 2)

Accepted Answer

public class LinkedListCycle{
    
        public static boolean hasCycle(ListNode head){
            if(head==null || head.next==null){
                return false;
            }
            ListNode slow = head;
            ListNode fast = head;

while(fast!=null && fast.next!=null){
                slow = slow.next;
                fast = fast.next.next;

if(slow==fast){
                    return true;
                }
               }
            return false;
        }
        public static void main(String[] args){
            ListNode head = new ListNode(1);
            head.next = new ListNode(2);
            head.next.next = new ListNode(3);
            head.next.next.next = new ListNode(4);
            head.next.next.next.next = head.next;
            boolean result = hasCycle(head);
            System.out.println(result);
        }

static class ListNode{
            int value;
            ListNode next;
            public ListNode(int value){
                this.value = value;
                this.next = null;
            }
        }

}

check if thelinkedlist has a cycle exceptions threads arrays - reverse pattern matching

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