How do you find the middle of a Linked List in one pass?

Difficulty: 3/10

two-pointer technique, linked list traversal, edge case handling

Finding the Middle Node

The standard one-pass solution uses slow and fast pointers. Slow advances one node at a time while fast advances two. When fast reaches the end, slow is positioned at the middle.

javascript

1
Time complexity: O(n).
2
Auxiliary space: O(1).
3
For an odd-length list, slow identifies the unique middle.
4
For an even-length list, this initialization returns the second middle node.
5
The choice of first or second middle can be changed by adjusting the pointer initialization or loop condition.

Scenario Questions

0-2 years experience

2-5 years experience

1Our service needs to split a linked list of user actions at the middle for parallel processing. How would you find the split point in one pass, and what edge cases would you guard against?

Follow-up Questions