C Language Cultivation

Chapter 90 The shortest path (5)

The devils that were everywhere intertwined and became a giant web. At least eight of the devils headed towards Lin Xun the moment he approached the glass door. Lin Xun's ears were filled with the whistling sound of the wind and the sound of weapons clashing against the devils' claws—these devils had hard and sharp claws that did not conform to the laws of biology.

The sword Qi scattered, shooting out in all directions with Lin Xun at the center, allowing him to resist the devils for a while.

But the sword Qi couldn't stop them forever; the consumption of sword Qi had limitations, and was directly related to Lin Xun's physical condition.

He didn't wish to stop them forever either. He used the long sword to slam straight into the glass door and was met by a strong counter-acting force; his wrist was numb, and he almost let go of the sword's hilt. The glass door—made of explosion-proof material—was indeed strong, and his attack only resulted to a spider web-like crack on the surface. He repeatedly beat it several times, and finally felt a slight dent on the glass surface, and the little white shadow on the other side of the door slowly approached.

But at this time, his wrist was already powerless and trembling, and it was glowing abnormally red.

Lin Xun looked at the white shadow and thought that he could disconnect from the Internet. No matter what level of devil this girl was, she wouldn't be able to kill him. Thinking about this, he made his decision and kicked the toughened explosion-proof door that was already densely covered with cracks!

With a clatter, the broken glass fell one after another, and Lin Xun also felt an indescribable pain in his knee joint—almost the same as the feeling of dislocation—but he could still walk.

The face of the white shadow was clearly displayed; the white dress, two braids on both sides of her head, and the familiar facial features, undoubtedly belonged to the girl—Lin Kexin—he met in the mental hospital. But what was different from that time was that her eyes were all covered in black; she walked out of the deep subway tunnel space like a lifeless puppet doll—the ghostly kind.

Apparently, she was being controlled by devils. When Lin Xun left that mental hospital, she was still like a normal girl. "Who is in her body now? That "invisible friend"? Does that mean, this invisible friend is the initiator of this trap?" After Lin Kexin said subway Line 4, that 'friend' tried to mislead everyone into the basement of that small building. Or was Lin Kexin colluding with her 'friend' and they set up this trap together?

The purpose of this trap was undoubtedly to wipe out the cultivators, and then kill Lin Xun in passing, or...was it just aimed at Lin Xun?

Lin Xun continued to fight with the devils while he was thinking; he knew that the fight would last for a while, and he shouldn't fight the devils near the subway track. He was physically mortal, and he couldn't contend with the subway train—that type of steel monster was equivalent to a thousand devils. So, Lin Xun retreated, taking a dozen steps back.

Lin Kexin also slowly walked out of the subway tunnel. She looked at Lin Xun directly, and the movements of the surrounding devils slowly stopped.

Lin Xun also looked at her.

He asked, "What are you going to do?"

Lin Kexin still stared at him, then tilted her head as if thinking about something.

Then, in the next second, her body rose to the air, rushing towards Lin Xun in a strange posture! She stretched out her right hand, her slender fingers hooked into a claw, and she rushed forward to grab Lin Xun's head! 

Although Lin Kexin was still a few meters away, the familiar prickling feeling appeared in his mind again, just like the day the system was damaged. He knew immediately that the devils would not negotiate with him, let alone shake hands and make peace. Their purpose was either to get something from him or put him to death.

At the same time, the other devils around him also flew up—thousands of black shadows enough to overwhelm the sky. It's unimaginable for one person to fight with thousands of enemies, and Lin Xun's power was not limitless. Indeed, as long as he was willing, he could wield any amount of sword Qi, and he could also wield a sword Qi of any strength, but the two cannot be done at the same time. To increase the amount of sword Qi, he must sacrifice its strength. But these devils were strong, and they also had the advantage of numbers—especially since Lin Kexin was among them, whose strength was unknown.

This was not mantis trying to stop a car (T/N: has a similar meaning with the proverb 'kick against the pricks'), but a small branch floating on the water, trying to block the floods of the Yellow River that is about to wash down from upstream.

But Lin Xun didn't panic.

The sword in his hand changed back to a keyboard.

Within two or three seconds between life and death, he called up a program, and at the speed that a programmer should have, he changed two parameters.

Some problems are unimaginable for humans, but not for computers. In the abstract sense, all concepts are mathematics.

Every devil had a position, which could be abstracted as a point in a three-dimensional space.

The sword in Lin Xun's hand was also a point.

A line can be connected between two points—the path of movement of the devils and his sword Qi, which was also a mathematical concept.

Then the whole scene can be extracted as a picture. 

In applied mathematics, there is a field called Graph Theory, and there is another kind of problem called combinatorial optimization problem. The laying of urban underground waterways; the planning of transportation routes; the cash flow in the financial network...all of these were within the scope of these two concepts.

How can Lin Xun block all the devils threatening his life with the fastest speed and fight Lin Kexin head-on?

And while attacking the devils, how can he ensure that the strength of the sword Qi is the greatest within the range he can achieve? 

The first problem was called the shortest path problem.

The second problem was called the maximum flow problem.

There are many algorithms to model and solve these two problems—Dijkstra, Prim, SAP, HLPP...

—This is mathematics and the application of mathematics.

Between the whistling of the wind, and that moment between life and death, Lin Xun looked as usual, and then he pressed the run button.

Sometimes, facing devils was like facing a final exam. Lin Xun's heartbeat was steady—because he was not an ignoramus.