What algorithm is used in package managers?

Question

Algorithms

I am writing my package manager in Python (similar to apt). Converted "Packages" files to SQLite database.
Now I can't figure out how to work with dependencies. For example: there are packages A,B,C,D,E...:
You need to download package D with all dependencies.
Package D depends on B;
Package B depends on A and C;
Package C depends on B;
Can you explain in simple terms the algorithm used in APT? Once I even found the names of the algorithm, now I can’t find it.

Answer 1

Cyclic dependencies (B → C → B) usually do not exist. But you need the dumbest search - for example, in depth.