Chapter 180: problem

There is a law in mathematics. The simpler description means the more difficult proof.
The p/np problem was first proposed by stevena.cook in 1971. In 2000, the Cray Institute of the United States announced it as one of the thousand problems, and it still hangs.
In 1971, 2000, and so far, countless mathematicians went on and on, trying to challenge it.
Lin never imagined before, these mathematics homes, including her father.
Even after she completely cleared the timeline, she realized that Laolin was interested in the p/np problem far before it became a millennium problem.
"Boss, come and listen to Coke." Lin was very happy, she was red-eyed and shouted.
The waiter cast a sigh, and she was too nervous, but she still used Coke and two plastic cups.
"Stinging", Lin opened the cans and poured two cups of Coke.
The foam overflowed to the mouth of the cup, and she and the old forest agreed to raise the cup. Subsequently. They drank a large cup in one go, put down the cup and wiped the mouth.
Lin Zhaoxi: "So, the paper published by Professor Feng, is there any proof...?"
"It's not officially published, it's just a draft, and it's going through the formal review process." Lao Lin made a slap of cola.
"You really have been paying attention to this!"
"Cough" Lao Lin squinted: "How do you give Dad a set?"
"Because I always feel that my father is holding me some things and deliberately not telling me."
"The imagination is too rich."
"Then why don't you tell me that you have studied p/np problems like Professor Zeng and you?"
"Pay attention to your wording, what makes me like them, obviously it is me first, and..." Old Linton paused and put up three fingers. "Three months ago, you knew what p/np, I am a philosophy with you." What are you talking about?"
Lin Chaoxi blinked and was once again stunned: "Are you a subject attack?"
Lao Lin "squats" twice, and is proud to not speak.
Lao Lin is right.
For her, this is a long exploration time spanning two time and space. For Lao Lin, three months ago, she was a liberal arts student with no interest in mathematics. He and her in mathematics, it is difficult to have a common language.
Fortunately, they can talk now.
About p/np, after the lecture that was hosted and translated, Lao Lin actually told her a lot.
If a problem can find an algorithm in polynomial time, then it is a p problem.
The np problem is that we can't find the answer in a quick way, but if we give a solution, we can verify it in polynomial time.
In the np problem, there is a particularly difficult problem called the npc problem.
The npc problem has two important characteristics: 1. It is an np problem; 2. All np problems can be reduced to it.
Stephena.cook published theplexitytheorem-provingprocedures in 1971, proposing the concept of the np-plete problem. And through the non-deterministic Turing machine, it proves that the satisfiability problem of the Boolean logic (sat problem) is an npc problem.
The entry point of Laolin's choice is the exact graph isomorphism.
The business in the noodle shop is not good enough. When they talk about it halfway, the red oil noodles come up. The noodle soup, with green and green onion, is very appetizing.
Lao Lin provoked a face and showed her: "Since the sat problem, a lot of npc problems have followed. To prove a new npc problem, you only need to reduce a known npc problem. Go to it, you can."
"It sounds a bit simple." Lin Chaoxi bite the chopsticks. "So why is the exact figure isomorphism not proven to be an npc problem?"
"There are two possibilities." Lao Lin said, "First, the exact graph isomorphism itself does not belong to the npc problem, so it cannot be proved."
"Second?"
"The second is of course that the mathematician's ability is not enough to prove it. What is the reason?"
"Oh..." Lin Chaoxi took a breath and asked, "Where is the specific difficulty, can you elaborate?"
"Where is the difficulty, first of all involves your understanding of the theory of graphs." Lao Lin Xing came, just put down the chopsticks and began to smash.
He said that Lin will listen carefully and ask if he doesn't understand.
Lao Lin said that he was rising, he ate two faces and chewed a few times.
The noodle shop is full of heat and the sound of Lao Lin is light and pleasant. In the meantime, Lin looked up, she saw Lao Lin’s smile. She even couldn't figure out for a moment, in which world she was.
A bowl of noodles almost finished, Lin Chaoxi was so hot and dripping.
From the content of Lao Lin, she probably knows what Lao Lin was trying at the time and how to prove the exact figure isomorphism belongs to the npc problem.
Even if she doesn't know Lao Lin, she is only an ordinary student. After sitting in the face with Lao Lin, she did not have to go to see the old paper that was accused of plagiarism. Lao Lin is an expert in this field, and he does not need to plagiarize other scholars' achievements.
Lao Lin is still very happy, the pleats in the corner of his eyes are deeper because he just looked old.
"I probably understand." She put down the chopsticks and drank the spicy soup: "So the proof of Professor Feng, is it right? You know?"
"You don't go to school to attend the graduation ceremony?" Lao Lin lit the phone and looked at the time. "Now the drop is still catching up."
Lin Zhaoxi’s brows were slight, and Lao Lin’s rare second interrupted her question about Professor Feng’s detailed proof.
"Graduation ceremony, no you are important," she said.
"It’s too nauseating."
"Why don't you ask me, who did you meet at Yongchuan University?"
"Who?"
"I have never met anyone."
Lao Lin: "..."
The noodle shop is steaming, although there is air conditioning, Lin Chaoxi still has a thin layer of sweat.
"I still have one last question." The cola in the cup had already been empty, and Lin held a cup of mouth for a half turn and looked up.
She asked: "Is this picture of Prof. Feng Deming's isomorphic paper related to the article you were accused of plagiarizing?"

Lin Xiangxi thought that her father had always been an open-minded person.
It’s indecent to tell her that you don’t have a mother, and that you can tell her where I can find out that he has been fired.
Now, Lao Lin has not only avoided two questions about Professor Feng. After her questioning, he stood up and went to the waiter to pay the bills and then walked out of the store.
The plastic curtain was opened and closed, and Lao Lin wore a formal suit shirt with obvious sweat on his back.
She took her eyes back and saw the carton he had forgotten to take away.

In the midsummer, the weather is hot, and all the splendid sunshine is screened through the leaves of the phoenix tree, leaving only a piece of light on the ground.
Alzheimer's patients forget that a carton brought by them is normal.
Lin Zhaoxi picked up the cardboard box and was amazed at its heavy weight. There is a logo of the accounting firm where Laolin is located on the box, which seems to be the material of the company.
The noodle shop is within walking distance of the Laolin company. She walked out the door and the old forest was gone.
She didn't think much about anything else. She walked to Laolin with a cardboard box and thought that Laolin probably went back to work, so she wanted to send things back.
Lao Lin seems to be so incomprehensible.
Even if she encounters questions such as ‘Is it if I have influenced your life’, Lao Lin will use the ‘national laws and regulations’ to fight haha.
He never used silence to refuse to answer.
The time is almost two o'clock, and the door of Laolin Company is quiet.
The front desk lady yawned in the sliding door, and Lin smiled at her with a cardboard box.
The sliding door opened and the air was blowing in the air. Lin Chaoxi played a spirit.
"Hello." The front desk lady immediately got up, polite and smiling, "Who are you looking for?"
"Ah, I am looking for..." Lin dynasty paused and changed his mouth, "Lin Zhaosheng."
"Ah, Lin accounting, he left today."
Lin Chaoxi held a cardboard box and stood still.
When I went out in the morning, Lao Lin’s rare suits and ties. She is still teasing Lao Lin, is she going to see the girl she likes, and now she wants to come, she is too stupid.
Probably because of leaving today, Lao Lin is very formal dressed. Older generations like him always have this habit.
Miss Front Desk: "Are you Lin Accounting?"
"I am her daughter." Lin returned to God.
"Sorry, I feel that you are a little bit stunned and have not recognized it before."
Because this is my second time here.
The front desk lady hurriedly poured a glass of water, came out and greeted her. "Would you like to sit down and call Lin to account?"
Lin was full of sweat, put down the cardboard box, and some embarrassed to take out the mobile phone, explained: "I just had food with him, he dropped a cardboard box in the store, I want to send him back."
There are indeed a few missed calls on the mobile phone, but not from the old forest, but the squad leader's life-saving serial call. The squad leader also sent her a few messages, "Why didn't you come to the graduation ceremony?" What happened?
She rushed back to the road - suddenly there was something in the house, sorry, sorry, you can help me with the next generation.
The squad leader did not reply the first time. The time was two o'clock in the afternoon. The graduation ceremony should officially begin.
Lin Zhaoxi put down the mobile phone and listened to the front desk lady. "The suitcases are all the draft papers that Lin accountant took away. It should be something your father wants to bring back. Everything else is given to us. Even the prickly pears he raised are not taken.

Lin Zhaoxi saw that the front desk did have a small fairy ball, which was a little malnourished, but the flower pot was very cute.
Didn’t take away any of the resignations, just take this carton? Lin Xixi looked at the seal that the box was closed at will, and I wanted to open it for a moment.
"The accounting draft papers are not all company secrets. You should be deducted when he leaves the job!" She laughed. "I moved almost tired."
"Yes, there is a lot of upstairs office. Our manager is joking that he actually wastes so much draft paper on the company and wants to deduct the money from the forest accountant!"
Lin Chaoxi just wanted to answer, and the phone flashed again.
What is it? What happened?
Lin Zhaoxi subconsciously picked up the mobile phone, but when she touched the screen, she found it difficult to reply. Finally, she could only put the phone down.
Just then, the hall moved the door open again, and the heat wave rolled in.
A middle-aged man in a suit and a trousers walked into the hall. The front desk lady quickly stood up: "Manager Zhang, are you coming back?"
Lin Daixi also subconsciously followed up.
"This is the daughter of Lin Accounting." The front desk lady introduced.
"Hey, Lao Lin's niece is so beautiful!" Manager Zhang looked very kind. He also saw her in the cardboard box on the coffee table. The reaction was very quick. "Lao Lin forgot to take it, and you gave her back?"
Lin Xiangxi nodded helplessly.

Hey.
Zhang took a few steps to the elevator and suddenly said to her,
I don’t want to visit your father’s office. You haven’t cleaned it.