Push Down Automata

Question

Construct a PDA for set of strings over {a,b,c,d} such that

L={ a^i b^j c^k d^l / i=k or j=l , i,j,k,l >=1}

Comments

will be NCFL

because, take cannot draw pda 2 strings like aabcc and bbdd

Answer 1

 

This a NCFL.

L={ a^i b^j c^k d^l / i=k or j=l , i,j,k,l >=1} Then This Language can be written like this

L = {a^i b^j c^i d^l  ∪  a^i b^j c^k d^j  } Here

L1 =   {a^i b^j c^i d^l}

L2 = { a^i b^j c^k d^j }

Then PDA  Will be 

Answer 2

We can construct a PDA for this one like- 1 pda which compares a's and c's and another one for b's and d's and Union them(or) so its acceptable by NDCFL

Another possibility- If we put condition like i=k AND j=l then at the same time we can't compare both so this one is not CFL and NDPDA or DPDA for this