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ECS 120: Introduction to Theory of Computation
Homework 7
Problem 1.
A
Stayput Turing Machine
is deﬁned as a TM which after reading/writing
to a tape cell can move the tape head either left, right, or leave it put in the same
cell. Show that a Stayput TM is equivalent to a TM. (Hint: Consider adding states
to the ﬁnite control.)
Problem 2.
Show that a
k
stack PDA (a
k
PDA), for
k
≥
2 is equivalent to a Turing
Machine.
Problem 3.
Specify fully a Turing Machine for the language
{
ww
R

w
∈ {
a,b
}
*
}
.
Problem 4.
Prove that a language
L
is decidable if and only if some enumerator enu
merates
L
in lexicographic order.
Bonus
A
kpebble machine
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This note was uploaded on 04/29/2010 for the course ECS 222 taught by Professor Mr. during the Spring '10 term at UC Davis.
 Spring '10
 mr.

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