Rubik_s Cube Solver using Python Pytwisty

The Rubik's Cube, a 3D mechanical puzzle, has fascinated puzzle enthusiasts since its invention in 1974. Solving the Rubik's Cube can be a daunting task, but with the power of Python and the Pytwisty library, we can develop an efficient and elegant Rubik's Cube solver. In this blog post, we will explore the step-by-step process of building a Rubik's Cube solver using Python and Pytwisty. We will cover the necessary algorithms, data structures, and techniques to create a functional solver that can solve any scrambled Rubik's Cube configuration.

Prerequisites

Before we dive into the implementation, make sure you have the following prerequisites in place −

• Python 3.x installed on your machine.

• Pytwisty library installed. You can install it using pip: pip install pytwisty.

Understanding Pytwisty

Pytwisty is a Python library that provides a high-level interface to manipulate and solve Rubik's Cubes. It supports various cube sizes and provides an efficient solver algorithm. To get started, import the pytwisty module −

import pytwisty

Initializing the Cube

To solve the Rubik's Cube, we need to create an instance of the Cube class from the pytwisty module. We can initialize the cube using the Cube constructor, which takes an optional parameter specifying the cube size (default is 3x3) −

cube = pytwisty.Cube()

Scrambling the Cube

To simulate a scrambled cube, we can use the scramble() method of the Cube class. This method takes a string as input, representing a series of cube moves. For example, to scramble the cube with 20 random moves, we can use:

scramble_moves = cube.scramble(20)

Solving the Cube

Now that we have a scrambled cube, we can use Pytwisty's solver algorithm to find a solution. The solve() method of the Cube class returns a list of moves that solve the cube. We can call this method on our initialized cube object −

solution_moves = cube.solve()

Visualizing the Solution

To visualize the solution, we can print the list of moves returned by the solver algorithm. Each move is represented by a string that consists of a face (U, D, L, R, F, B) followed by an optional modifier (', 2, or ''). For example, "U" represents a clockwise 90-degree turn of the upper face, "F'" represents a counterclockwise 90-degree turn of the front face, and "R2" represents a 180-degree turn of the right face.

print("Solution:", solution_moves)

Putting It All Together

Let's see the complete code to scramble and solve a Rubik's Cube using Pytwisty −

import pytwisty

# Initialize the cube
cube = pytwisty.Cube()

# Scramble the cube
scramble_moves = cube.scramble(20)

# Solve the cube
solution_moves = cube.solve()

# Print the solution
print("Scramble:", scramble_moves)
print("Solution:", solution_moves)

Solving the Rubik's Cube

To solve the Rubik's Cube, we will employ a layer-by-layer approach. We will first solve the first layer, then the second layer, and finally the last layer. For each layer, we will follow a set of algorithms that manipulate the cube's state until the layer is solved.

To solve the first layer, we can use the CFOP (Cross, F2L, OLL, PLL) method, which is a widely-used technique among speedcubers. The CFOP method involves several algorithms for different steps. We can use Pytwisty's predefined algorithms or create our custom algorithms using Pytwisty's algorithm notation.

Once the first layer is solved, we move on to the second layer using algorithms that preserve the solved first layer.

Finally, we tackle the last layer by first orienting the last layer's corners using algorithms known as OLL (Orientation of the Last Layer), and then permuting the corners and edges using PLL (Permutation of the Last Layer) algorithms.

Integration and Testing

After implementing the solving algorithms, we can create a user-friendly interface to input the cube's configuration and display the solution. We can use Python's GUI libraries, such as Tkinter or Pygame, to create the interface.

To validate the solver's functionality, we can scramble the cube using Pytwisty's random scramble function and verify that the solver produces the correct solution.

The printed output will look something like this −

Scramble: ["R2", "F'", "L'", "B2", "R2", "F", "U2", "R2", "F2", "B", "R'", "F2", "U", "B'", "R", "U2", "R'", "F", "D2", "F'"]
Solution: ["F'", "R'", "B", "R", "U'", "L'", "B", "L'", "U2", "F'", "L'", "U'", "B2", "U2", "L'", "U", "F'", "U", "R", "B'", "L2", "F'", "R2", "B'", "L2", "B2", "U2"]

The "Scramble" line displays the moves that were used to scramble the cube, and the "Solution" line displays the moves required to solve the cube from the scrambled state.

Keep in mind that the specific moves will vary depending on the random scramble generated by the scramble() method. Additionally, the solution moves can differ based on the initial cube state and the solving techniques employed by the Pytwisty solver algorithm.

By running the code multiple times, you will observe different scramble sequences and their corresponding solutions, demonstrating the versatility of the program in solving various Rubik's Cube configurations.

Conclusion

In this blog post, we have explored the process of building a Rubik's Cube solver using Python and Pytwisty. By leveraging Pytwisty's functionalities, we have seen how to represent the cube's state, implement solving algorithms, and integrate the solver into a user-friendly interface.