1. CS252: Systems Programming
Ninghui Li
Topic 22: Regular Expressions and Finite State Automata

2. See Slides from External Sources

3. Clicker Question 1 (SQL)
Given 4 tables:
Product (pname, price, category, manufacturer)
Purchase (buyer, seller, store, product)
Company (cname, stock price, country)
Person(per-name, phone number, city)
To find the names of people who bought American products, how many tables need to joined together in a SELECT statement? 1 2 3 4
The query cannot be answered using these tables.

4. Clicker Question 2 (DFA)
What regular language is accepted by the following DFA?
abca
a(bc)+a
abc(bbc)*a
abc(bbc)+a
None of the above b a b c a q0 q1 q2 q3 q4

5. Clicker Question 3 (DFA)
What regular language is accepted by the following DFA?
abc(c*)
(ac|b)c*
a(b|c)+
b|ac(c*)
None of the above q1 b e c q0 q2 q3 a e

6. Clicker Question 4 (For fun)
You are given a biased coin, which will given head with a certain probability p, where the exact value of p is unknown. If you want to use this coin to make an unbiased binary decision, i.e., decide Yes with probability ½, what is the minimal number of times you need to throw your coin to do so?
A. 1 B. 2 C. 3 D. 4 or higher
E. It cannot be done