NIELIT 2018-33

Question

The language $\{ W^a X^b Y^{a+b} \mid a, b, >1\}$ is

• A. Regular
• B. Context-free but not regular
• C. Context sensitive but not context free
• D. Type$=0$ but not  context sensitive

Answer 1

Is answer B? Because we can push W and X into the stack and for each Y we can pop one element of the stack.That means we can design a PDA for this grammar

Answer 2

B is correct. Its CFL or Type 2 language.

Push a for each W. Push a for each X. Pop a for each Y. If the stack is empty then it is accepted else not.

Answer 3

It is context free grammar but not regular because it requires to solve one stack of memory.