package arithmetic.com.ty.binary;

public class LinkedCycle {
    /**
     * 判断是否有环
     * 
     * @param head 链表头节点
     */
    public static boolean isCycle(Node head) {
        Node p1 = head;
        Node p2 = head;
        while (p2 != null && p2.next != null) {
            p1 = p1.next;
            p2 = p2.next.next;
            if (p1 == p2) {
                return true;
            }
        }
        return false;
    }

    /**
     * 链表节点
     */
    private static class Node {
        int data;
        Node next;

        Node(int data) {
            this.data = data;
        }
    }

    public static void main(String[] args) throws Exception {
        Node node1 = new Node(5);
        Node node2 = new Node(3);
        Node node3 = new Node(7);
        Node node4 = new Node(2);
        Node node5 = new Node(6);
        node1.next = node2;
        node2.next = node3;
        node3.next = node4;
        node4.next = node5;
        node5.next = node2;
        System.out.println(isCycle(node1));
    }
}

    /**
     * 计算环长
     */
    public static int cycleLenth(Node head) {
        Node p1 = head;
        Node p2 = head;
        int count = 0;
        int length = 0;
        
        while (count < 2 && p2 != null && p2.next != null) {
            if(count > 0) {
                length++;
            }
            p1 = p1.next;
            p2 = p2.next.next;
            if (p1 == p2) {
                count++;
            }
        }
        
        return length;
    }