Questions
5 of 16
1How do you merge two sorted Linked Lists?
2What is a Sentinel Node/Dummy Node? Why is it useful?
3What is an XOR Linked List? Why is it rarely used?
4Why is insertion/deletion at the head of a Linked List O(1)?
5How do you find the middle of a Linked List in one pass?
6Explain the difference between a Linked List and an Unrolled Linked List.
7How do you detect a cycle in a Linked List? (Floyd's Tortoise and Hare)
8How do you reverse a Linked List? (Iterative and Recursive)
9Why does the standard library (Java/C#) not heavily feature Linked Lists? (Cache locality issues)
10How do you copy a Linked List with random pointers? (Deep Copy)
11Explain why QuickSort is preferred over MergeSort for Arrays, but MergeSort is preferred for Linked Lists.
12What are the types of Linked Lists? (Singly, Doubly, Circular)
13Why is accessing an element in a Linked List O(n)?
14What is a Linked List? How does it differ from an Array?
15When would you choose a Linked List over an Array?
16What is a Skip List? How does it improve search time?
Data-StructuresData-Structures
Basics
Complexity Analysis
Arrays and Strings
Linked Lists
Stacks and Queues
Hash Tables
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How do you find the middle of a Linked List in one pass?

Finding the Middle Node

javascript
  1. 1

    Time complexity: O(n).

  2. 2

    Auxiliary space: O(1).

  3. 3

    For an odd-length list, slow identifies the unique middle.

  4. 4

    For an even-length list, this initialization returns the second middle node.

  5. 5

    The choice of first or second middle can be changed by adjusting the pointer initialization or loop condition.

Difficulty: 2/10

Follow-up Questions

  • ❓How do you return the first middle for an even-length list?
  • ❓Can this technique be used for cycle detection?