Leetcode 题目解析之 Linked List Cycle

    public boolean hasCycle(ListNode head) {

        if (head == null) {
            return false;
        }

        ListNode slow = head;
        ListNode fast = head.next;

        while (fast != null) {

            if (fast.next == null || fast.next.next == null) {
                return false;
            }

            if (slow == fast) {
                return true;
            }

            fast = fast.next.next;
            slow = slow.next;
        }

        return false;
    }