Recall & Review
beginner
What is the main goal of the Reorder Linked List problem?
To rearrange a singly linked list so that nodes are ordered as: first node, last node, second node, second last node, and so on.
Click to reveal answer
intermediate
Which three main steps are used to solve the Reorder Linked List problem efficiently?
1. Find the middle of the list.<br>2. Reverse the second half.<br>3. Merge the two halves alternating nodes.
Click to reveal answer
beginner
How do you find the middle node of a singly linked list?
Use two pointers: a slow pointer moves one step at a time, and a fast pointer moves two steps. When fast reaches the end, slow is at the middle.
Click to reveal answer
intermediate
What is the purpose of reversing the second half of the linked list in the reorder process?
Reversing the second half allows easy merging from the end towards the middle, enabling the alternating order required.
Click to reveal answer
intermediate
What is the time complexity of the reorder linked list algorithm using the three-step approach?
O(n), where n is the number of nodes, because each step (finding middle, reversing, merging) takes linear time.
Click to reveal answer
What does the fast pointer do when finding the middle of a linked list?
✗ Incorrect
The fast pointer moves two steps at a time to reach the end faster than the slow pointer.
Why do we reverse the second half of the linked list in the reorder process?
✗ Incorrect
Reversing the second half helps merge nodes from the end in alternating order.
After finding the middle, what is the next step in the reorder linked list algorithm?
✗ Incorrect
The second half is reversed before merging.
What is the final step in the reorder linked list algorithm?
✗ Incorrect
Merging the two halves alternating nodes creates the reordered list.
What is the space complexity of the reorder linked list algorithm?
✗ Incorrect
The algorithm uses constant extra space by rearranging pointers in place.
Explain the three main steps to reorder a singly linked list.
Think about splitting, reversing, and merging.
You got /3 concepts.
Describe why reversing the second half of the list is necessary in the reorder linked list problem.
Consider how to access nodes from the end easily.
You got /3 concepts.