Hello, I want to ask...

What design plattern is needed to solve my problems below?

P1.

Input -> ProcessA -> ProcessB -> ProcessC -> Output

Suppose Process A, B, C might use different alogorithm to solve,

e.g. ProcessA (A1, A2, A3), ProcessB (B1, B2), ...

so my program should be flexible enought to change the alogroithm on
runtime.

P2.

Similar to P1, but when some algorithms are selected, the flow
changed, e.g.

If I use A1, I can only use B2, but not B1

So considering both as 2 questions, what kind of plattern you would
suggest?

thanks.