c++:如何在不使用库的情况下序列化/反序列化对象?

I am trying to understand how serialization/deserialization works in C++ without the use of libraries. I started with simple objects but when deserializing a vector, I found out, that I can't get the vector without having written its size first. Moreover, I don't know which file format I should choose, because, if digits exist before vector's size I can't read it right. Furthermore, I want to do that with classes and map containers. My task is to serialize/deserialize an object like this:I am trying to understand how serialization/des