Implement recursive algorithms with sub-workflows: Towers of Hanoi demo

How it works

This is an example of using sub-workflow nodes and a proof of concept showing that it’s possible to solve and explain recursive problems with n8n.

Towers of Hanoi - Task

Move a stack of n disks from rod A to rod C, using rod B as auxiliary. Only one disk can be moved at a time, and no disk may be placed on a smaller disk.

Example

n=4
     |          |          |
     =          |          |
    ===         |          |
   =====        |          |
  =======       |          |
 ---------  ---------  ---------
     A          B          C

Algorithm

procedure Hanoi(n, X, Y, Z):
  if n == 1:
    move disk from X to Z
  else:
    Hanoi(n-1, X, Z, Y)
    move disk from X to Z
    Hanoi(n-1, Y, X, Z)

Notes

• This is a learning example. In a real scenario, you would probably use an iterative approach with only a single code node.
• When experimenting with recursion, make sure to define a termination condition first. Also, be aware of the "Restart workspace" link in the n8n Dashboard.
• Learn more about Recursion on Wikipedia.

Set up steps

• Optional: Set "numberOfDiscs" in node "Set number of discs"
• Execute workflow