my question is as it is odd length palindrome , so it can be ababa , right ?
Now , in the given diagram , they have not mentioned the scenario :
1) when a is the stack top element and input symbol is b ( b , a / ? )
2) when b is the stack top element and input symbol is a ( a, b / ? )
Now , my question is - without these two transitions can we design this pda ? ( as it is done in the given ans )
According to me this question is unclear but if we thinks that ∊ represents that at the top of the stack there can be anything then only we can say option c is correct ..
But in gate they will not ask such unclear and confusing question...
at state B
there should be following transitions specified..
∱(B,b,Zo)=(B,bZ0) , ∱(B,a,Zo)=(B,aZ0) , ∱(B,b,b)=(B,bb), ∱(B,b,a)=(B,ba),
∱(B,a,a)=(B,aa) , ∱(B,a,b)=(B,ab)
Hope this will clear your doubt...