Chapter 148: Simple solution of 1 stroke

"Euler Seven Bridges?"
Ying Yingying has a cute look on her face, "This...I just heard about it, but I don't know what it is."
Just when Cheng Nuo was about to explain, Li Shiye, who had been sitting on the side without saying a word, spoke slowly.
"At the beginning of the 18th century in Königsberg, Prussia, a river crossed, and there were two small islands on the river. There were seven bridges connecting the two islands with the river bank. Someone asked a question: how can a walker not repeat , Without omission, walk through seven bridges at once, and finally return to the starting point. This is the famous Euler Seven Bridges problem. But the Euler Seven Bridges problem itself has no solution."
"At that time, the famous mathematician Euler transformed the Euler Seven Bridges problem and formed a new concept-one-stroke drawing! He put forward all two sufficient conditions to satisfy the one-stroke drawing."
"One, all points on the graph are even points."
"Second, the figure has only two singular points, and all the remaining points are even points."
"The same is true for converting flat graphics into three-dimensional graphics." Li Shiye raised his chin and pointed to the two people participating in the challenge on the screen and said, "So, the two of them don't need to have each graphic in mind. , The route of each point is walked all over. Just by observing whether the point of the irregular solid polygon is an even point or a singular point, you can judge whether it can be drawn in one stroke!"
Cheng Nuo next to him has a black line.
Sister, you’re forced to pretend, what am I pretending?
"But..." Li Shiye changed his tone at the end, "Even so, the difficulty of this project is still very high. Every point on the irregular three-dimensional polygon, the two of them need to confirm it again before they can make their own judgments. ."
"Although the difficulty of this challenge project is not as complicated as it seems on the surface. It is definitely not worth 8 points!"
Obviously, Li Shiye said this to Cheng Nuo.
"But I just think this challenge project is very simple!" Cheng Nuo's mouth was flat and I looked aggrieved.
Li Shiye was also amused by Cheng Nuo. He pointed to the screen in front of him and said, "Well, since you think this project is simple, please invite Cheng Nuo to tell me about the three-dimensional polygon that Sun Meng is currently observing. , Is it a one-stroke three-dimensional polygon?"
On the screen, Sun Meng from Peking University is standing in front of a three-dimensional polygon, frowning in thought.
Although it only needs to judge whether all the points on the solid polygon are even points, or there are only two singular points, it is a lot of work for the brain of ordinary people.
There are seventeen or eight points on a three-dimensional polygon.
At every point, the player needs to observe it. See if the number of line segments connected by this point is odd or even.
If it is an odd number, this point is a singularity. If it is an even number, this point is an even point.
Counting down such a line segment, if there are more, a three-dimensional polygon, the player needs to count more than 100 line segments, a very large number!
The shape of the polygon in front of Sun Meng at this time was obviously a little more complicated than the other ones observed.
Therefore, it took longer for Sun Meng to observe.
In the lounge, Cheng Nuo simply glanced at the screen, and the data about the irregular three-dimensional polygon Sun Meng was observing appeared in Cheng Nuo's mind.
There are 26 points, 38 line segments, 24 even points, and 2 singular points.
Look at the data and meet the second one-stroke condition. The number of singularities is 2.
and so……
Cheng Nuo replied casually, "This polygon can be drawn in one stroke."
Li Shiye glanced suspiciously at Cheng Nuo. Since the camera on the screen switched quickly, he didn't have time to verify Cheng Nuo's answer, and he didn't know if Cheng Nuo was right.
"What about this one?" Li Shiye continued to ask.
The camera on the screen has switched to Zhang Zheng's side, and Zhang Zheng is also frowning in front of an irregular three-dimensional polygon to observe.
Cheng Nuo simply glanced at the screen again, as if he hadn't been observed and calculated, and then gave his own answer in the next second, "This can't be a single stroke."
Li Shiye glanced sideways at Cheng Nuo. Since the camera stayed on Zhang Zheng for a long time, it was enough for Li Shiye to judge whether the three-dimensional graphics on the screen could be drawn in one stroke.
Seven or eight seconds later, Li Shiye turned to look at Cheng Nuo and sighed, "You are right."
He observed five points of this irregular solid polygon. It is found that three are singular points and two are even points.
The result is already obvious, this three-dimensional polygon cannot be drawn in one stroke!
What made Li Shiye feel puzzled was that even he took seven or eight seconds to judge.
But why can Cheng Nuo give the answer instantly with just a glance?
This is not scientific!
On the screen, student Zhang Zheng from Tsinghua University, after observing the irregular three-dimensional polygon in front of him for nearly twenty seconds, shook his head slowly and denied the answer.
At this time, the lens cut to the sky, giving a panoramic view of the 200 irregular three-dimensional polygons.
A huge stream of data slowly emerged in Cheng Nuo's eyes, and then transmitted to Cheng Nuo's brain.
No. 1 solid polygon with 21 points, 29 line segments, 6 singular points, and 15 even points.
No. 2 solid polygon with 18 points, 25 line segments, 2 singular points, and 16 even points.
…………
No. 200 solid polygon with 26 points, 35 line segments, 4 singular points, and 24 even points.
The lens only gave two or three seconds of panoramic time.
But two or three seconds was enough for Cheng Nuo.
Soon, the camera switched back to Sun Meng of Peking University.
Sitting aside, Li Shiye still wanted to speak, repeating the previous question, but was interrupted by Cheng Nuo in advance. "Student Li Shiye, I know what you want to ask me."
"In order not to trouble you one by one, I will answer you all at once."
Cheng Nuo smiled faintly, and said unhurriedly, "Of the 200 irregular three-dimensional polygons on the field, there are a total of 45 that meet the conditions of one stroke."
"Numbers, they are No. 2, No. 6, No. 11, ... No. 198!"
"How about, Li Shiye, are you satisfied with this answer?"
Cheng Nuo looked at Li Shiye and said with a smile.
"You..." Li Shiye stared at Cheng Nuo blankly. After a long silence, he suffocated a word, "These...you didn't make up all of these, right?"
It's not that Li Shiye has to think so, but Cheng Nuo's performance is a bit too much.
That's 200 solid polygons!
It's him~EbookFREE.me~ to observe it all over again, it is impossible without ten or twenty minutes!
How long did Cheng Nuo take? A few seconds!
How can it be possible to observe all 200 graphics in a few seconds?
Facing Li Shiye’s doubts, Cheng Nuo just shrugged,
I’m right or not, you’ll know in a while.

…………
Every haircut is like gambling, this time...I lost the bet!
So ugly~~~
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