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91Ó°ÊÓ

Let ∑=0,1. Let B be the collection of strings that contain at least one 1 in their second half. In other words,

a. Give a PDA that recognizes B

b. Give a CFG that generates B .

Short Answer

Expert verified

a

b

S→XY
X→AB
Y→A1A|A1B|A1X|B1X|X1X

A→00*|ε
B→11*|ε

Step by step solution

01

Explain Context-free Grammar and Pushdown Automata

Context-free grammar generates context-free languages. The regular

languages are the subset of the context-free languages that are an identical

set of languages accepted by pushdown automata.

02

Give a PDA that recognizes B

a Consider the given,

Construct the pushdown automata P to determine the language B . The P can be

defined as (Q,∑,τ,δ,q0,F)wherelocalid="1662190593189" Q=q0,q1,q2,∑=0,1,τ=x,F=q2

The PDA is as follows,

a

03

Give a CFG that generates B .

Consider the given,

The CFG for the language is as follows,





The String S has the production of XY concatenation. The string X can consist of

any number of 1’s and 0’s that are represented by A and B . The string Y may

consist of at least only one 1 or one 1.

Therefore, the Context -free Grammar for the language B has been obtained.

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