Can you recommend a novel that is set in the 70s to 90s, about a crazy university mathematics lecturer and a young genius?

It was a book that he had read a long time ago. He had a deep impression of it, but he had forgotten its name.
Male Lead: Young Genius (me), Madman University Mathematics Instructor (also a genius), a little girl of similar age
[Location: Hospital]
The Mad Lecturer was once a young and talented man. He said that he had a theory. After speaking for a long time, he realized that someone had done it decades ago. He felt that the world was laughing at him, so he went crazy and entered a mental hospital.
However, the young man didn't know that one day, the lecturer met the young man and realized that he was very smart. He taught him questions from trigonography to advanced mathematics every day. The young man learned it and every time he went in, he saw a dark red liquid at the corner of the lecturer's mouth. Later, the nurse said that this person was crazy and not a lecturer. He thought about how the flowers in the flower bed were always being eaten, and he got scared. Then he didn't go to the lecture that day. The lecturer kept calling his name. After an hour, he was very scared. When the lecturer started to talk about the questions, it was as if someone was really listening. He confirmed that the lecturer was crazy. Then, on the day he was discharged from the hospital, he saw the hospital dog eating flowers in the flower bed. Only then did he realize that something was wrong.
There was once a little girl who was afraid of the hospital, so she slept in the same bed as him. They agreed not to be separated. After being discovered, the nurse asked them to be separated. She looked at them strangely, but their feelings were really pure.
Many years later, the young man was diagnosed with cancer during the day. He was very afraid, but later found out that it was a mistake. The cancer was his old colleague who had drawn blood with him.
My colleagues don't want to believe it, they say it's impossible, it must be you
His colleague's hair was very dark. He was 50 years old and still had dark hair. He thought of that university teacher. The teacher said at that time: You are young white (young white?) Ah
He felt that the hospital looked familiar, especially the triangular plum.
He checked the file and found that there were a few years of blank records for his colleagues. It was those years, and they had the same surname as the professor. He asked if you were XXX. You have been to this hospital before. I am XX. Do you remember?
The colleague was stunned for a moment, but he denied it firmly.
The teenager had told him the story during the day, but his colleague said it was definitely not him.
When he left, the nurse said, It's strange, not a single strand of white hair.
The little girl from back then had met him again. Although she had said that she would never be afraid if she was always together when she was young, that was all.
There was a line in the book that went like this: Maybe he wasn't crazy.(He was normal when we didn't think he was crazy.) When we really thought he was crazy, he really was crazy.
I was only in the fourth or fifth grade at that time, so I don't remember it after nine years. Although the content was heavy and satirized society, it left a deep impression. He remembered that the book was from the same series as "Half of a Man Is a Woman"…Looking at the description of the environment (it was quite a big hospital, but the environment in the book looked simple and crude now) and the title in the book, it should be from the same period of time, but it would take place in the city, around the 1980s?
He had read so many books, but it was rare for him to remember so many details. However, he hadn't read it carefully at that time, so he really wanted to read it again.

Answer 1

I recommend a novel called " The God of Rebirth, the Top Student " to you. It's about an unemployed mathematics doctor who was reborn in 1982 after an accident. He became a college entrance examination repeater and became an all-rounded gold medal lecturer. He helped his students from failing to getting top grades and even helped them solve various problems. If you are interested in the 70s and 90s, this novel is also worth reading. I hope you like my recommendation.😗