Where can I read about linear algorithms (C language)?

Question

C++ / C#

Please tell me where you can read more about linear algorithms, there are a couple of tasks but I don’t know how they can be implemented (I don’t have much experience), for example:
A two-digit number is given. Get the number formed by permuting the
digits of the given number.

Answer 1

What is there to read? A linear algorithm is a sequence of operations without conditional branches and loops. That is, just a chain of steps, always performed strictly in turn in the same order.