I am too Lazy to update about me.

Yes a pda can have two accepting/final states. If you look at the Formal definition of a PDA,

A PDA is formally defined as a 7-tuple:

where

is a finite set of states

F is the set of accepting states, that means it can be any number of accepting states but should be a subset of Q.

Please explain how many binary trees (structurally different) can be formed using n unlabelled nodes by using just the concept of combinations and not directly using the formula of Catalan Numbers.

#include<stdio.h>

#include<conio.h>

void main()

{

int i=25;

clrscr();

printf("%d",scanf("%d",&i));

getch();

}