CS3800 Fall 2022 HW 6
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CS3800 Fall 2022 HW 6
Be sure to note the location of each problem in Gradescope
Problem 1
For each of the following sets, give the smallest complexity class in which it is contained. Classes are listed from smallest to largest. Write your choice A through D under each numbered language and give a short justification. Your choices are:
A. DECIDABLE
B. UNDECIDABLE but RECOGNIZABLE
C. UNDECIDABLE and UNRECOGNIZABLE but its compliment is RECOGNIZABLE
D. UNDECIDABLE and both it and its compliment are UNRECOGINZABLE
I: {(M, x, y) l M accepts x and rejects y}
II: {(M1, M2 ) l M2 rejects every input that M1 accepts}
III: {(M1, M2 ) l 3 x, y such that M1 accepts x and rejects y, but M2 rejects x and accepts y} IV: {(M)l M only rejects strings beginning with 0}
V: {(M, w) l M accepts w using only lwl2 tape cells}
VI: {(x) l x = 0(M) , (M) e K or x = 1(M) , (M) K}
(Here 0(M) denotes the concatination of 0 and the encoding of M . Recall also K = {(M)l M accepts (M)} .)
Problem 2
Formally prove that L 丈m L for any undecidable L. (L is also denoted Lc .)
Problem 3
Show that for any two languages A and B there is a language J where A <T J and B <T J.
Problem 4
Let L = {(M) l L(M) = { ‘X’ } }. Prove that
L <T HALT.
2022-10-25