Rule department scholar

……

It took Zhao Yi more than ten minutes to carefully compose the post, and then posted it directly, and then advertised, shouting in the group.

"My post! Cape Forum!"

"Please help!"

When people in the group saw the news, they clicked on the link and glanced at it, and then they were attracted by the content.

Gossip is just one aspect.

As professional technical geeks, their interests and hobbies are obviously different from those of ordinary people. Most of them glance at the front and directly look at the final data.

The group soon became lively.

Intelligent Technology Zhang Junlei: "This calculation is very complicated!"

Ma Xiaojun, a missionary of Neo-Confucianism: "It doesn't seem difficult to design a program with a computer, does it?"

Zhang Zhen, who is not a storyteller: "It's hard, the data is too huge, I can't figure it out in a short time."

Ma Xiaojun, a science missionary: "I do research and dive first."

Smart Technology Zhang Junlei: "Why don't you just ask Zhao Yi?"

Science Missionary Ma Xiaojun: "I am a Doctor of Science!"

Smart Technology Zhang Junlei: "So you're embarrassed to ask a high school student? Can you understand it this way? / Haha"

Zhang Zhen, who is not a storyteller: "Don't always tell the truth, be a little hypocritical, be reserved, pay attention to being reserved! / Haha"

Zhao Yi looked at the chat messages and felt a little helpless.

The point! ?

He was arguing with people, and everything was on the hot search list. When people in the group saw the post, why did it turn into a technical discussion?

Fortunately, the people in the group are pretty reliable.

Everyone's focus is on algorithm communication, but I still help to forward it, and they each have a certain influence.

For example, Zhang Zhen sent it directly to the company's group.

The message from the manager must be opened.

Ma Xiaojun, a science missionary, is a returnee doctor of science. He was hired by the Capital University of Technology as a lecturer, and his position is also an associate professor. He is qualified to lead graduate students.

He sent it to the student group.

Other people in the group who saw the news, saw such a 'gossip' and 'technical' post, and they also helped forward it.

repost, repost...

The post is connected in the penguin group and spread rapidly.

After Zhao Yi read the chat in the group, he simply played the game, swiped the remaining 'leisure coins', and then returned to the browser to refresh the post, and found that it was already very popular.

Click: 8267.

Reply: 249.

He began to read the reply patiently.

turn a page.

Turn another page.

Then, turn another page.

The posts in the front row are almost all 'technical exchanges', some ask about algorithms, some provide algorithm opinions, and some disagree on algorithm opinions.

Then, the controversy began.

Zhao Yi flipped through more than a dozen pages in a row, and found that there were more people talking about technology than gossip, but he didn't post to discuss the Rubik's Cube algorithm with others, but to prove that what he said had evidence and reasons.

The wind direction of public opinion has been taken astray!

Fortunately, there are always the most gossip people. Most non-technical people are not interested in algorithms. What they care about is whether the conclusions are true.

As long as the conclusion is true, it proves that there may be something wrong with the game.

Most gossip people believe that if Zhao Yi dares to present the data, the conclusion must be true.

You can't go wrong with science and math.

There are many replies on the algorithm controversy, but no one said that the result was wrong, and a few people said that the difficulty of restoring Jia Hongning's Rubik's Cube is indeed less than Zhou Junkai's through unscrupulous estimates.

……

Seeing this, Zhao Yi also discovered the problem.

Calculating the least steps of Rubik's Cube is not a simple matter.

Although he gave the answer directly, he couldn't give the calculation process. The process given in "The Law of Contact" is to use the simplest way to manually restore the Rubik's Cube, rather than how to calculate the minimum steps.

"Do you want to take a video to prove it?"

It works.

Just take a video of turning the Rubik's Cube, and use fixed steps to scramble the Rubik's Cube that has been restored to six sides, and turn it into the Rubik's Cube in the show, which directly proves the conclusion.

but……

This proof is not rigorous.

"Even if you take a video and manually restore the Rubik's Cube, it can only prove that the fixed number of steps can be restored, but it cannot prove that it is the minimum number of steps."

Math is rigorous, science is rigorous.

This is where the problem lies.

Zhao Yi went to search for the Rubik's Cube calculation, and soon discovered a bigger problem. The calculation of the minimum number of steps to restore the Rubik's Cube turned out to be a problem that has plagued the scientific community for decades.

The minimum number of steps to restore the third-order Rubik's Cube, there is a term called - the number of God!

The appearance of God's Number is mainly because the calculation of the lowest step of the third-order Rubik's Cube is too large, and the possibility of steps is astronomical. It cannot be simulated by a computer, and it is impossible to give an accurate minimum number of steps to restore.

In 1992, the German mathematician Kosenba proposed a new idea of ​​finding a method to restore the Rubik's Cube, which greatly reduced the calculation amount of Rubik's Cube restoration.

Three years later, according to the method proposed by Kosenba, the scientist Reid entered it into the computer for improvement. Through calculation, he found that the "Number of God" would not exceed 26.

However, Kosenba's calculation method is not rigorous, and what he obtained from his thinking may not be the best way to restore it, so the calculation of "God's Number" is also very likely to be overestimated.

However, without introducing Kesenba's idea, the amount of calculation is too huge.

This problem has never been resolved.

Zhao Yi smiled wryly and said to himself, "So, my brain can count the world's problems?"

"Not right!"

Calculating the lowest steps of a single definite Rubik's Cube reduction, and calculating the "God's Number" are not at the same level of difficulty. The different forms of the third-order Rubik's Cube are astronomical figures--

43.

If you only calculate one of them, the difficulty is relatively simple, but if you only use the exhaustive algorithm, the amount of calculation is still quite huge.

That is definitely not desirable.

This is also the reason why many people discuss algorithms in the group and below the post.

Zhao Yi stared at the screen and fell into thought.

If there is no effective, accurate, and publicly recognized calculation method, the results given in his post will be meaningless. At most, he will add a video to prove that he can indeed restore it in fixed steps.

But the other party still had something to say.

It is best to use a scientific and strictly forbidden method, so that the other party has nothing to say at all.

"Then design an algorithm and directly calculate the minimum steps to restore each fixed form Rubik's Cube!"

"If it can be designed, it will be called a 'magic cube calculator'?"

"As long as you input the color of the small grid on the fixed surface of the Rubik's Cube, you can figure out how to use the fewest steps to turn the Rubik's Cube back..."

Chapter 73 Keys to Algorithm Design

To design an algorithm to solve the third-order Rubik's Cube, two points must first be clarified.

One is input data.

The input data is the six faces of the three-dimensional Rubik's Cube, corresponding to the nine grid colors. The data is characterized by six colors, and each color is nine in total. In addition, the color corresponding to the middle of the six faces is fixed. .

The second is to output data, which is the purpose of calculation, to obtain the minimum steps required to restore the Rubik's Cube.

As long as this condition can be met, other desired data, such as the process of realizing the lowest steps, are just simple records made by the way during the operation of the program.

After clarifying the input and output data, the front and rear frames are almost out.

This is similar to the algorithm package sent by Zhang Zhen, but the level of difficulty has been increased by dozens, hundreds of times, or even higher.

Next, the design begins.

modeling.

Modeling is to turn real problems into mathematical problems, and use mathematical formulas and codes to express the relationship between the small cells of the Rubik's Cube and the possible conversion methods.

There are two ways of doing this.

One is based on the spatial position, that is, the color will change when the position is fixed; the other is based on the fixed color small grid to form a position change.

After choosing a good modeling method, enter the real design process.

Zhao Yi just started to think, and encountered a huge problem: how to determine that a twist is to make the magic direction approach the restored direction, instead of making it more chaotic?

This is a super problem.

Cracking this problem is almost equivalent to completing the algorithm.

Therefore, this way does not work.

Think again.

Then think about it from another angle, you can find the faces with the most same color, and use this as the basis to realize the restoration. Just like most people’s choice, restore one face of the third-order Rubik’s Cube first, and the rest will become much easier.

However, science is rigorous.

How to prove that starting from the face with the most same color, the restoration speed is the fastest?

How to prove that restoring one face first is the fastest?

Zhao Yi just started designing the program, and encountered a lot of problems. He took a deep breath, and his logical thinking ended here.

Next comes causal thinking time.

Zhao Yi understood the difficulty of algorithm design, so he opened the system interface and simply used a scientific research coin.

[Scientific research currency: 15. 】

[Use scientific research coins to enhance causal thinking. 】

[Scientific research currency -1, assists in improving causal thinking ability, and obtains the effect of inspiration.Duration: 10 [-] minutes. 】

moment.

Mindsets have changed.

Zhao Yi stared at the computer screen again, and his thinking jumped. Instead of entangled in the problems he thought of, he jumped to the data analysis of the input Rubik's Cube.

For example, based on the center color of each side, the minimum number of steps required to convert the small grids of the same color on other sides to the corresponding center side.

For example, how many grids are next to grids of the same color, as well as their specific positions, must be recorded in detail.

and many more.

After consuming scientific research coins to improve the causal thinking mode, the use of "Law of Karma" and "Law of Contact" became subconscious. Convert to code on keyboard.

write.

Write again.

An hour has passed.

Zhao Yi pressed his forehead hard, and his brain felt extremely tired. He glanced at the energy value: [Energy: 61/104. 】

No wonder!

After glancing at the code on the screen, he gritted his teeth and used four learning coins.