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DataWeave programming challenge #4: Solve the Tower of Hanoi mathematical puzzle

In this post:

This challenge is based on the Tower of Hanoi mathematical puzzle - this is a tough one!

Try to solve this challenge on your own to maximize learning. We recommend you refer to the DataWeave documentation only. Try to avoid using Google or asking others so you can learn on your own and become a DataWeave expert!

⚠️ Important: There are 3 different scenarios to test your code is working properly and to ensure there are no hardcoded values. However, only the first scenario is provided in the Playground link below. Please copy+paste the other two scenarios to make sure your solution is working properly.

## Input

Consider the following JSON inputs:

SCENARIO 1

```
{
"moves": 0,
"disks": 3,
"targetTower": "C",
"towers": {
"A": [
1,
2,
3
],
"B": [],
"C": []
}
}
```

SCENARIO 2

```
{
"moves": 0,
"disks": 4,
"targetTower": "C",
"towers": {
"A": [
1,
2,
3,
4
],
"B": [],
"C": []
}
}
```

SCENARIO 3

```
{
"moves": 0,
"disks": 7,
"targetTower": "Y",
"towers": {
"X": [],
"Y": [],
"Z": [
1,
2,
3,
4,
5,
6,
7
]
}
}
```

## Explanation of the problem

Create a DataWeave script to solve the Tower of Hanoi puzzle. The input payload contains the number of moves (starting at 0), the total number of disks in the game, the target tower where all the disks have to be moved, and the 3 towers containing each disk.

(You can use this link to play the game online)

Here are the rules of the game:

With each move, you can only move one disk at a time from its current stack to a different stack.

You can only place smaller disks on top of bigger disks. For example, you can place disk 1 on top of disk 3 but you can't place disk 5 on top of disk 2.

You can only move the disk at the top of any stack.

## Expected output

For each of the three scenarios from the input, these are the expected outputs:

SCENARIO 1

```
{
"moves": 7,
"disks": 3,
"targetTower": "C",
"towers": {
"A": [
],
"B": [
],
"C": [
1,
2,
3
]
}
}
```

SCENARIO 2

```
{
"moves": 15,
"disks": 4,
"targetTower": "C",
"towers": {
"A": [
],
"B": [
],
"C": [
1,
2,
3,
4
]
}
}
```

SCENARIO 3

```
{
"moves": 127,
"disks": 7,
"targetTower": "Y",
"towers": {
"X": [
],
"Y": [
1,
2,
3,
4,
5,
6,
7
],
"Z": [
]
}
}
```

## Clues

If you're stuck with your solution, feel free to check out some of these clues to give you ideas on how to solve it!

## Answer

If you haven't solved this challenge yet, we encourage you to keep trying! It's ok if it's taking longer than you thought. We all have to start somewhere ✨ Check out the clues and read the docs before giving up. You got this!! 💙

There are many ways to solve this challenge, but you can find here my solution. I'm sure you all can make it better! :) Mine is super long 😂

Solution

I also recorded myself coming up with the solution, but without explanations. Just some lo-fi music and a screen :) you can leave the video in the background while working! :D let me know if you find this useful.

Feel free to comment your code below for others to see! 😄

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Actually in this challenge, we are just asking minimum number of moves required to solve it.

So just simple logic can solve this. But as I saw your Solution you have performed algorithm. There are couple of things in that a beginer like me can't get like @Lazy. And one more thing in other programming languages we avoid to use "do {} " but here you are using it alot why? any advantages.

One of my favorites mathematical puzzles! Here's a simple solution, without really moving individual disks :)

Really cool challenge!😄

I think there are some open questions which should be described in the problem statement:

- Are there always 3 towers?

- Is the initial state of the towers always like in your sample inputs? So all disks are in order on another tower than the targetTower.

- Is it possible that there are two rings with the same number? (Probably not, but should be stated explicitly IMO)

I will try my luck with the challenge and post my solution (if I solve it 😂).