It's not only Hao Yun's parents who are watching CCTV interview, but also Hao Yun's three sons in the 401 bedroom, plus a little fat man Zhou Xuan who always comes to the 401 side to sleep.

"Brother Yun, Niupi! This has to break the Guinness world record for the fastest time to hand in papers in the hope cup competition? " Looking at Hao Yun coming out of the gymnasium, Zhou Xuan couldn't help shouting.

"And the record?" Asked Liang Ziyuan.

"Hey, hey, we can apply for one for him." Zhou Xuan is embarrassed to say with a smile.

"But what the moderator said... The main examination committee is in a meeting. What are you going to discuss?" Zheng Xueqian felt his chin and frowned.

"I don't know. Maybe I wrote some wonderful answers." Zhou Xuan shrugged his shoulders, but said.

Amazing answer?

What's the answer?

Including Zhou Xuan himself who threw out this sentence, the people around the computer were all curious.

At the same time, Professor Li Xuesong, who was reading his paper in the office of several colleges of Jiangcheng University, suddenly received a call from Xia Guo Institute of mathematics.

The caller is Professor Liu Shoufeng, a big bull in the field of number theory in China. He is also the author of the last big question in the previous undergraduate mathematics competition.

Professor Li Xuesong was too lazy to answer the caller ID on his mobile phone, but he thought that the old man was not so careful, so he patiently pressed the connect button.

"Hello? What's the matter, Lao Liu? "

"Did you see the email I sent you?"

"Mail?"

"Just sent it to you!"

I don't know what medicine is buried in the old man's stomach. Professor Li Xuesong opened his mailbox full of doubts and saw an unread email.

Good guy, one minute ago?

It's not that wechat has a message to remind you that ghost can't see your email!

He rolled his eyes and opened the e-mail, but Professor Li Xuesong, who saw the contents, was stunned.

The text has only a string of characters with unknown meaning -- 0x5f375a86

"Is this a hexadecimal number?" Touching his chin, Professor Li Xuesong's face was filled with expressions of interest, "is there any mystery about this number?"

Every time Liu Shoufeng, an old man, calls him, there are only two things, either to show off or to share the latest discovery. As usual, he could see some clues, but after watching this number for a long time, he even quietly changed the decimal system and binary system in his heart, and didn't feel anything different.

Professor Liu Shoufeng on the other end of the phone laughed: "sure enough, even you can't see what's special about this number!"

"You old man, don't be so fussy. If you have a fart, let it go at once. If it's OK, I'll hang up!" Professor Li Xuesong said with a smile.

"Hang up? Then you will regret it! I'm not bullshit with you. Do you remember the Newton Raphson method? "

"Nonsense, who can't remember that!"

Newton Raphson method, which was put forward by Newton in the 17th century, is a method of approximate solving equations in real number field and complex number field. Although these people who study pure mathematics rarely use this method, this method is widely used in the field of computer.

For example, if you want to calculate the value of √ 2, you can guess a number casually, for example, 4. There is no doubt that √ 2 cannot be equal to 4, but as long as you use Newton's iterative method to iterate continuously, after n steps of iterative operation, you can always calculate 1.414. And if you use 2 as a guess, because 2 is close enough to 1.414, you only need two iterations to figure it out.

Li Xuesong remembers that he seemed to have talked about this piece of knowledge more than once in class with computer majors, but he really didn't know what to dig into.

Professor Liu Shoufeng: "I just sent you an email. There is an algorithm that has been translated into mathematical language. You can see why I am so surprised at this number after reading it."

Hearing this, Professor Li Xuesong couldn't help rolling his eyes, but he couldn't resist his curiosity and opened the next email as he said.

The whole algorithm itself is not difficult, but just find the reciprocal of the square root. Professor Li Xuesong even felt that even if he did not translate it into the language of mathematics, he could fully understand it.

In short, the 0x5f375a86 is a constant used to calculate the guess value.

Because using Newton iterative algorithm to find the reciprocal of square root first needs a guess value, which is usually determined by a series of calculations according to the user's input value.

Professor Li Xuesong made up a random number and tried to use the algorithm to find the reciprocal of the square root.

But just then, something magical happened!

He found that no matter what value he input, the guess value calculated by the system is extremely close to the final result, so that the whole algorithm only needs to be executed twice at most to end the cycle.

And the reason for all this is that 0x5f375a86!

"Incredible..." gradually discovered the mystery, Professor Li Xuesong muttered to himself, "how was this number discovered?"

He's full of one question now.

Why is it 0x5f375a86?

Professor Liu Shoufeng said in a joking tone: "I have to ask you. After all, it's your students' trouble."

Hearing this, Professor Li Xuesong was shocked.

"My students? Are you sure? "

What the hell?!

Why didn't I know I had such a strong student?

"The player named Hao Yun is not your student?" Suddenly, it seemed like something came to mind. Professor Liu Shoufeng patted his head and said, "Oh, I almost forgot that the one you name is the main examination committee of Mathematics Competition... Hope cup is engaged in programming. It seems that it really has nothing to do with you."

"Wait, Hao Yun? Hope cup? What does that mean? " Professor Li Xuesong asked after him in a misty way.

Professor Liu Shoufeng patiently explained: "in short, I hope there is a topic in the cup competition, which requires to improve the operation efficiency of a software. So far, your student has done it, and the solution has surprised everyone. Usually, the idea of code farmers should start with code, right? As a result, he directly went to modify the code of the underlying function, so that the function that originally needed to be calculated several more steps to be understood was now solved in two steps. "

Professor Li Xuesong was stunned, and it took him a long time to say a word.

"... is it so awesome?"

"Yes, it's more than bullshit. None of those old guys from the main test committee understood what this number was, and then sent an email to our Xia Guo Institute of mathematics. As a result, I didn't see any fame after reading it for a long time."

With that, Professor Liu Shoufeng sighed and continued.

"It reminds me of the famous Basel problem, the damned infinite series ∑ 1 / n ²。 No one knows why it was first discovered to converge to π²/ 6 people, will be bored to remember π²/ 6. You know that special is irrational number, who has nothing to remember that? But the irritating thing is, he just knows! And it turned out to be true later! "

"We have to admit that some people in this world are really sensitive to numbers, even beyond the ordinary people's understanding, to the extent of intuition... At least, before talking to your student face-to-face, I can only explain that now!"

meanwhile.

Shanghai is thousands of miles away.

The reporter's little sister, who was crouching outside the rest room of the gymnasium, finally got the chance to open the door.

Without any hesitation, she immediately caught a man in a plaid shirt coming out from backstage.

Look at his face and dress, it should be a software engineer.

In this way, we may know something inside!

"Hello, sir, I'm a reporter of CCTV education program. May I interview you? What kind of answers did the contestant submit, so that the main test committee needs to hold a meeting to discuss... Is there any news that can be disclosed?" The reporter asked curiously.

The man didn't want to be interviewed, but after seeing the logo on the microphone, he hesitated and finally said.

"The competition is still going on, and I can't reveal too many details. As for the contestant you said... What's surprising about him is that his answer can only be said to have changed one number."

"One, one number?" The reporter was shocked.

Even the photographer behind her had a surprised look on her face.

"Yes... I'm also surprised. It's totally unexpected? Maybe it will affect not only the glacier engine, but also the products in other fields. "

When he said this, the man who was supposed to be a software engineer was dignified and helpless.

"Anyway, it's beyond what I know. After a while, the professors from the Department of mathematics of Xiadong Normal University will come, and they seem to have set up a temporary expert group there. You might as well ask their opinions, which may give you a reasonable answer? "