Day of Imprisonment

Based on the actual situation analysis, the 'building' itself is a stage, a stage specially prepared by the former Luo Xi for the later Luo Xi.

This stage has no hints, no explanations, no rules; everything needs to be discovered by oneself.

Even if one is not perceptive enough, they might not even realize that this place is a stage.

He would do it this way, so the former him would definitely do it too.

"There can't be the slightest bit of luck, there can't be any negligence; use this stage to constantly consolidate this concept, because the 'Cocoon Breaking Project' is crucial and cannot tolerate any mistakes," Luo Xi muttered to himself at this moment.

He continued to explore every room in the building.

Just as he thought, this was a building that was already uninhabited, but many rooms still had traces of people having lived there.

Teacher Han had said that he vaguely remembered living in a building, and Luo Xi would often come to chat with him.

Unsurprisingly, the building that Teacher Han was talking about was this place.

Moreover, Luo Xi could be sure that there was definitely more than just Teacher Han in the building at that time, but now, everyone had left.

Did they leave on their own, or did he make them leave?

Above the fifteenth floor, the elevator could no longer reach, which should be some kind of restriction or protection mechanism.

But even the fifteenth floor had close to a hundred rooms.

Luo Xi carefully examined every room, and at the same time, he collected all the keys he could find in the rooms, and finally returned to the first floor, arranging all the keys neatly on the ground, looking like rows of soldiers waiting for inspection.

Looking at these one hundred and twenty keys that were completely identical in shape and size, Luo Xi smiled.

Without a doubt, his direction was correct.

If the keys found were of various kinds, there might be a problem, but if the keys found were completely the same, then there was no need to ask; the key he was looking for was among them.

Luo Xi arranged all the keys according to the room numbers.

How to find the correct key was the first difficult problem.

In fact, there was a very simple, completely brainless method for this.

That was to try them one by one.

But Luo Xi would not do that.

Because if he designed this puzzle, he would definitely prevent this completely brainless method, and even set a deadly trap for the possibility of someone trying to do so.

For example, setting the number of attempts for each door.

If the number of attempts exceeded a certain number, five times, or three times, it would directly trigger the death trap.

These settings were to prevent trying with a stupid method.

"120 keys come from 92 rooms, 64 of which have only 1 key, and 28 have 2 keys. According to the number of keys found in the rooms, there may be two situations: the real key may only come from those 64 rooms, which is a 64-choose-1; the second situation is that the real key is among the 56 keys found in those 28 rooms, which is a 56-choose-1."

Luo Xi was thinking about various possibilities of this puzzle.

It could be said that just choosing the correct key was already very difficult.

But in this stage specially designed for himself, finding the key was only the first step; later, he still needed to choose the correct one from the 5 doors, and then use the chosen key to open the door.

Possibly, there was only one chance.

This kind of stage, if placed outside, would definitely be unsolvable.

It was possible that no one could crack it at all.

Even Luo Xi was lost in thought at this moment.

He was thinking about another question.

Did the stage in this building also follow the principle of 'checkpoint stage' design?

That is, fairness and justice!

"The reason why a principle is called a principle is that it cannot be easily changed, and I will not cheat when designing the stage. Then, even the checkpoint stage that looks difficult will have a way to solve it, and there must be hints in some details; otherwise, it will not conform to the principle of fairness and justice."

After Luo Xi confirmed this point, he completely immersed his attention in this stage.

At this moment, everything outside would no longer become his interference.

The matters in Fairy Tale Town, Lin Qiqi, An Zhiyan, Hao Xiuwen, and Zhang Zhe, Luo Xi left them all behind.

He was only doing one thing now.

Solve this puzzle, pass this checkpoint stage that he specially designed for himself.

Luo Xi first divided the 120 keys into two parts.

The keys from the 64 rooms were on the left, and the keys from the 28 rooms were on the right.

"Based on the rooms, eliminate keys with a low probability."

Luo Xi almost immediately made the next judgment.

Since the keys and the rooms were strongly bound, and the keys themselves were exactly the same, with no difference that could be seen, even if two were put together, it was impossible to compare who looked different from whom, then find what differences and differences there were between them and the objects they were bound to.

This binding object was naturally the room.

"The rooms in the entire building can be divided into two categories: inhabited and uninhabited."

Luo Xi had discovered this when he explored the rooms earlier. Some rooms did have traces of people living there, such as beds and some obvious daily necessities.

And the uninhabited rooms could also be seen at a glance.

Interestingly, in all the rooms, all the keys were placed in very obvious places, that is, on the table in the room.

Just from this point, it could be clearly seen that this was indeed a well-designed checkpoint stage.

"On the side of the 64 keys, 47 rooms are inhabited, and 17 rooms are uninhabited; on the side of the 28 keys, 23 rooms are inhabited, and 5 rooms are uninhabited."

In this way, all the keys were classified again.

"47, 17, 46, 10. There is only one real key, which must be in one of these four categories. First of all, I eliminate uninhabited rooms!"

Luo Xi almost immediately made the first elimination.

His basis was very simple.

The uninhabited rooms were all clean, with nothing but the most basic bed, table, and desk lamp.

Without clutter, there were no clues. These keys in the rooms without clues should naturally be eliminated.

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In this way, he had to find the correct one from 47 keys and 46 keys.

Luo Xi's gaze moved back and forth between the two piles of keys.

The corresponding rooms were 47 and 23.

And the scene of each room, at this moment, was like a series of rapidly flashing continuous images, flashing quickly in Luo Xi's mind.

This was an extremely brain-intensive process.

Even Luo Xi was frowning, and sometimes, he would rub his temples with his fingers, his eyes seemed to have lost focus, and his pupils were very dilated. If he sat there motionless, someone might even mistake him for a corpse.

For a long time.

"It's books!"

Luo Xi compared all the remaining rooms. On the desks where the keys were found, there were actually all kinds of messy things, papers, pens, rulers, and books.

There was more than one book.

Among them, there were actually the two books that Luo Xi was very familiar with.

They were "The World of Players" and "Memory".

It could be said that every inhabited room had these two books, but not all of them were placed on the table. Some only had one, some had two, and some were not placed on the desk, but in the drawer or the bookshelf next to it.

Luo Xi quickly made another elimination based on this.

The basis was that he only wanted the rooms with two books on the table at the same time.

There were 24 rooms and 15 rooms respectively.

The corresponding keys were 24 and 30.

At this moment, in Luo Xi's brain, the appearance of all the rooms was like an album opened at the same time. All the 'photos' were arranged to form a huge picture, like a scene in a 'spot the difference game'.

With the rooms being eliminated to this number, these 'memory photos' of the rooms were difficult to see the difference at a glance.

It could be said that this was the highest difficulty 'spot the difference game'.

"Freeze the desk. The key to truly solving the key selection problem is only on the desk."

Luo Xi suddenly looked up.

His eyes showed an unprecedented firmness.

If someone looked at his eyes at this moment, they seemed to be able to see, within his pupils, desk scenes that looked similar arranged together.

"If you don't look at the keys, or even the other things on the table, and only focus on the two books, the positions of "The World of Players" and "Memory" are different, and some are opened, and some are closed."

"Eliminate the rooms with closed books."

Luo Xi had entered his own specific problem-solving state at this moment, truly reaching a state of absolute concentration.

If you only look at the desks with these two books in the open state, that is, the corresponding rooms, then the number of candidates will be sharply reduced.

"73!"

This was the number of rooms remaining after a series of eliminations.

The corresponding number of keys was 7 and 6.

From the initial 120-choose-1, now, the range was narrowed to 13-choose-1.

It had been reduced by nearly ten times.

Luo Xi was naturally very excited. For him, who had an almost obsessive love for solving puzzles, his adrenaline was soaring at this moment, and he was already extremely excited.

But even so, he still had to find the only one from the 13 keys.

In addition, there might be errors in the elimination rules used before. If there was a problem in any link, such as making a mistake in the elimination method, it would lead to failure.

Just as Luo Xi was carefully recalling what was different about the two books in those ten rooms, he suddenly realized something.

He immediately got up and ran towards the elevator.