Final Exam Study Guide, Math 421, Fall 2019

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Examinable Material (Course Coverage)
  1. The three handouts to supplement the textbook:
    1. Self-Referencing, Uncountability and Uncomputability in CPSC 421;
    2. this article on the Myhill-Nerode theorem;
    3. notes on sneaky complete languages.
  2. Sipser's Textbook:
    • Chapter 1, excluding the Pumping Lemma in 1.4.
    • All of 3.1, the part of 3.2 on multi-tape and non-deterministic Turing machines.
    • All of 4.2.
    • The part of Chapter 5 about reducing an undecidable language to another language, L, to show that L is also undecidable (see notes from 10_21 and 10_23).
    • All Chapter 7, except the definition of NP as a polynomial time verifiable language; we defined NP only as a language decidable by a non-deterministic T.m. in polynomial time.
    • All of 8.1 and 8.2.
    • 9.2: Oracle machines: notation, (e.g., P^A = poly time with oracle A) and basic properties. co-NP, P^SAT. Theorem: P^B = NP^B for any PSPACE-complete problem, B (second half of Theorem 9.20, the Baker-Gill-Solovay Theorem), including the "one line" proof: P^B ⊂ NP^B ⊂ NPSPACE ⊂ PSPACE ⊂ P^B .
  3. Remarks and additional material:
    • We introducted SNEAKY-NTM = { < M,w,1^t > | M accepts w within time t } which is NP-complete. An analogously defined SNEAKY-PSPACE = { < M,w,1^s > | M accepts w within space s } is PSPACE-complete. (Hence we know a PSPACE-complete language even though we did not cover Section 8.3.)
Practice Problems for the Final Exam All homework problems and the problems on the midterm are good practice problems.

Below I list the problems that directly correspond to the material learned this year in the language that we used.

Here are some problems for which I will provide partial or full solutions: Here are some problems with some brief solutions:
  • Final 2004, Problems 1,2,5,6,7,8,9. For 9(b) the hint--in the terminology we used this year--is to use the Myhill-Nerode theorem. (solutions).
Here are some problems for which I will not provide solutions: Some problems from the Final 2017 were discussed on 11_29.

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