Recall & Review
beginner
What is a doubly linked list?
A doubly linked list is a chain of nodes where each node has three parts: data, a pointer to the next node, and a pointer to the previous node. This allows moving forward and backward through the list.
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beginner
What happens when you delete the last node from a doubly linked list?
The last node is removed, the second last node's next pointer is set to null, and the list's tail pointer is updated to the second last node.
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intermediate
Why do we need to update the previous node's next pointer when deleting from the end of a doubly linked list?
Because the new last node should not point to the deleted node, so its next pointer must be set to null to mark the end of the list.
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intermediate
What is the time complexity of deleting the last node in a doubly linked list if we have a tail pointer?
O(1) because we can directly access the last node using the tail pointer without traversing the list.
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beginner
Show the steps to delete the last node in a doubly linked list with nodes: 1 <-> 2 <-> 3 <-> null
1. Identify the last node (3).<br>2. Set the next pointer of node 2 to null.<br>3. Update the tail pointer to node 2.<br>Resulting list: 1 <-> 2 <-> null
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What pointer must be updated when deleting the last node in a doubly linked list?
✗ Incorrect
The previous node's next pointer must be set to null to mark the new end of the list.
If a doubly linked list has only one node and you delete from the end, what happens to the list?
✗ Incorrect
Deleting the only node makes the list empty, so head and tail pointers become null.
What is the time complexity of deleting the last node if no tail pointer is maintained?
✗ Incorrect
Without a tail pointer, you must traverse the list to find the second last node, which takes O(n) time.
Which pointer in the last node of a doubly linked list is always null?
✗ Incorrect
The next pointer of the last node is always null because there is no node after it.
After deleting the last node, what should the tail pointer point to?
✗ Incorrect
The tail pointer should update to the new last node to keep the list consistent.
Explain the steps to delete the last node from a doubly linked list and update pointers correctly.
Think about what happens to the node before the last and the tail pointer.
You got /4 concepts.
Describe how the presence of a tail pointer affects the efficiency of deleting from the end of a doubly linked list.
Compare with singly linked list deletion from end.
You got /4 concepts.