Conceptual doubt

#1

sir,can you tell me weather in subset based recursion problem like above we should think by pmi approach or first thinking of recursion tree and then building our logic?

#2

this is the first step in case u see that there is some recursive structure
to solve a particular question

i did not get this term,. wht is it?

#3

pmi means principle of mathematical induction

#4

no no dude use recursion tree to question which have some type of recursive approach
i to havent ever used pmi to think of it