Catalan number doubt'

#1

for n=0 how the ans is 1
whats a NULL tree ?

#2

forming no tree
is the only alternative

when the root node is NULL that is a NULL tree

#3

I hope I’ve cleared your doubt. I ask you to please rate your experience here
Your feedback is very important. It helps us improve our platform and hence provide you
the learning experience you deserve.

On the off chance, you still have some questions or not find the answers satisfactory, you may reopen
the doubt.