beyond-interviews/analysis/04-reverse-linked-list/diagrams/README.md

Reverse Linked List — PlantUML Diagrams

This directory contains PlantUML diagrams for the three-pointer linked list reversal algorithm.

The diagrams use a small list:

1 -> 2 -> 3 -> null

and show how it becomes:

3 -> 2 -> 1 -> null

Files

• 00_initial_state.puml — initial state before the loop
• 01_save_next.puml — saving next = current->next
• 02_reverse_current_link.puml — reversing current->next
• 03_move_pointers.puml — moving previous and current
• 04_second_iteration.puml — state after the second node is processed
• 05_final_state.puml — final state after the loop

Generate PNG Files

plantuml diagrams/*.puml

Generate SVG Files

plantuml -tsvg diagrams/*.puml

Core Idea

During the loop, the list is logically split into two parts:

• previous points to the already reversed part
• current points to the node currently being processed
• next temporarily preserves access to the remaining original list

The key operation is:

current->next = previous;

But this is only safe after saving:

Node* next = current->next;

Otherwise the remaining part of the original list would be lost.