Floyd의 알고리즘은 연결 목록의 루프를 어떻게 감지합니까?

<code class="java">boolean hasLoop(Node first) {
    if (first == null) {
        return false; // List does not exist, so no loop
    }

    Node slow, fast; // Create two references.
    slow = fast = first; // Make both refer to the start of the list.

    while (true) {
        slow = slow.next; // One hop.

        if (fast.next != null) {
            fast = fast.next.next; // Two hops.
        } else {
            return false; // No loop.
        }

        if (slow == null || fast == null) {
            return false; // No loop.
        }

        if (slow == fast) {
            return true; // Loop detected.
        }
    }
}</code>