Linked lists

Track ownership of every link before rewriting it.

Understand the problem

Use a dummy node to simplify operations at the head. For reversal, save next, redirect current.next to previous, then advance. Slow and fast pointers expose midpoint and cycle structure.

Trade-offs and pitfalls

Pointer manipulation uses little extra memory but is easy to break through update ordering.

Check your understanding

Explain Floyd cycle detection and why meeting does not necessarily occur at the cycle entry.

Your study notes