Check Cyclic Linked List

#include <stdio.h>
#include <assert.h>

typedef struct Node {
    Node* next;
} Node;

bool checkCylic (Node* head) {
    Node* slow = head;
    Node* fast = head;
    if (head == NULL) return true;
    while (fast->next != NULL) {
        slow = slow->next;
        fast = fast->next;
        if (fast->next != NULL) {
            fast = fast->next;
        } else return false;
        if (fast == slow) return true;
    }
    return false;
}

int main ()
{
    Node head1, node1;
    head1.next = &node1;
    node1.next = NULL;

    Node head2, node2, node3, node4;
    head2.next = &node2;
    node2.next = &node3;
    node3.next = &node4;
    node4.next = &node3;

    assert (checkCylic(&head1) == false);
    assert (checkCylic(&head2) == true);

    return 0;
}