Middle of the Linked List
Recognize the pattern
Brute force idea
A straightforward first read of Middle of the Linked List is this: Count length, then traverse to length/2 — two passes. That instinct is useful because it follows the prompt literally, but it usually keeps revisiting work the problem is begging you to organize.
Better approach
A calmer way to see Middle of the Linked List is this: Slow moves 1, fast moves 2 — when fast reaches end, slow is at middle — single pass. The goal is not to be clever for its own sake, but to remember the one relationship that keeps the solution grounded as you move forward.
Key invariant
The truth you want to protect throughout Middle of the Linked List is this: Fast moves twice as fast, so when it finishes, slow has covered exactly half. If that remains true after every update, the rest of the reasoning has a stable place to stand.
Watch out for
A common way to get lost in Middle of the Linked List is this: Off-by-one for even-length lists — decide if you want the first or second middle node. Most mistakes here are not about syntax; they come from losing track of what your state, pointer, or structure is supposed to mean.