Question 17 (3 points) Which of the following code snippets correctly initializes a circular singly linked list that uses a dummy head node? head = NULL; head = new Node; head->next = head; head->prev = NULL; head = new Node; head->next-head: head->next = head; head - new Node; head->next = NULL; Question 18 (3 points) When inserting a new node, given by the pointer newNode, into a singly linked list and the predecessor node pointer, pred, is given, which of the following code snippets correctly performs the insertion? Assume pred is not NULL. After the insertion, newNode should become the successor of pred in the linked list. O pred->next = newNode->next; new Node->next = pred; newNode->next - pred; pred->next = newNode->next; pred->next = newNode: newNode->next-pred->next; newNode->next-pred->next; pred->next = newNode; Question 19 (3 points) What is the time complexity of the most efficient algorithm that determines if an item is contained in a sorted list implemented via a linked list? O(1) O(log n) O(n) O{n log n) None of the above Question 20 (3 points) What is the time complexity of the most efficient algorithm that determines if an item is contained in a sorted list implemented via an array? O(1) Odlog n) O(n) O{n log n) None of the above