Recursive Algorithms with Sub-workflows: Towers of Hanoi Demo

This n8n workflow demonstrates how to implement recursive algorithms using sub-workflows, specifically showcasing the classic Towers of Hanoi puzzle. It utilizes the "Execute Sub-workflow" node to simulate recursive calls, making complex problems manageable and modular.

What it does

This workflow acts as a foundational example for recursive logic in n8n. While the provided JSON is a skeleton, its structure indicates the following intended steps for a Towers of Hanoi implementation:

1. Trigger: The workflow can be initiated either manually or by another workflow (acting as a sub-workflow call).
2. Input Processing: An "Edit Fields (Set)" node would typically prepare the necessary parameters for the recursive function (e.g., number of disks, source peg, destination peg, auxiliary peg).
3. Base Case Check: An "If" node is crucial for any recursive algorithm. It checks for the base case (e.g., if there's only one disk to move).
4. Recursive Calls (Sub-workflows): If the base case is not met, the "Execute Sub-workflow" node would be called multiple times, simulating the recursive steps of moving n-1 disks, then moving the largest disk, and finally moving the remaining n-1 disks. Each call would pass updated parameters.
5. Code Execution (Optional): A "Code" node could be used for more complex logic, state management, or output formatting within the recursive steps.
6. Output: The final result or a specific action would be performed once the recursion unwinds.

Prerequisites/Requirements

• n8n Instance: A running n8n instance (self-hosted or cloud).
• Understanding of Recursion: Familiarity with recursive algorithms is beneficial to fully grasp the workflow's purpose.
• Sub-workflow Setup: To fully implement the Towers of Hanoi, you would need to create a separate sub-workflow that this main workflow calls recursively. The JSON provided is for the calling workflow, not the sub-workflow itself.

Setup/Usage

1. Import the workflow: Import the provided JSON into your n8n instance.
2. Create a Sub-workflow: Design a separate n8n workflow that represents the "recursive function" for the Towers of Hanoi. This sub-workflow should:
   • Start with an "Execute Workflow Trigger" node to receive input from the main workflow.
   • Contain an "If" node to check for the base case (e.g., numDisks === 1).
   • If not the base case, it should call itself (or rather, the main workflow which then calls it again) via an "Execute Sub-workflow" node with modified parameters, simulating the recursive steps.
   • Perform the "move" action (e.g., log a message like "Move disk from A to B") for the base case or the largest disk.
3. Configure "Execute Sub-workflow" nodes: In the main workflow, configure the "Execute Sub-workflow" node(s) to point to the ID of your newly created sub-workflow.
4. Define Inputs: Use the "Edit Fields (Set)" node to define the initial parameters for the Towers of Hanoi puzzle (e.g., numDisks, sourcePeg, destinationPeg, auxiliaryPeg).
5. Activate and Execute: Activate the workflow and execute it manually to see the recursive calls in action in the execution logs.