User Klaus Draeger

10 votes

Accepted

Why is the set of all regular expressions classified as context-free, instead of regular?

answered Nov 16, 2015 at 14:41

10 votes

DFA for accepting all binary strings of form power of $n$ (not divisible by $n$) i.e. $n^k$ for given $n$

answered Jan 22, 2016 at 17:24

9 votes

Unprovable Post correspondence problem instance

answered Mar 27, 2015 at 18:20

9 votes

Accepted

What does least fix point and greatest fix point mean in Safety games

answered May 12, 2015 at 12:31

7 votes

Loop variant for a while loop that occasionally doesn't decrease?

answered Nov 9, 2015 at 0:12

7 votes

What are the simplest examples of programs that we do not know whether they terminate?

answered Jul 30, 2015 at 14:08

6 votes

Accepted

Can we check in polynomial time if the language of a DFA is closed against Kleene star?

answered Apr 28, 2015 at 13:47

6 votes

Accepted

Term rewriting; Compute critical pairs

answered Sep 16, 2015 at 20:06

5 votes

Regularity of unary languages with word lengths the sum of two resp. three squares

answered May 22, 2015 at 14:30

5 votes

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Construct Turing Machine which accepts the language $ww$

answered Jun 16, 2015 at 13:47

5 votes

Accepted

Efficiently finding $k$ smallest elements of Cartesian product

answered Sep 7, 2015 at 18:50

5 votes

Why is GFp -> GFq false in LTL, even though GFp and GFq are false?

answered Jun 29, 2012 at 23:08

5 votes

What can be said in general about a homomorphism between two regular languages?

answered Feb 19, 2016 at 13:16

4 votes

Accepted

What happens to uninterpreted predicates in Ackermann's reduction?

answered Jan 26, 2016 at 13:02

4 votes

Show that some context free languages must contain more that one non-terminal

answered Dec 29, 2015 at 15:19

4 votes

Accepted

CTL* query evaluation order

answered Mar 7, 2017 at 14:25

4 votes

Accepted

Proving the loop invariant for a simple program in Hoare logic

answered Mar 17, 2017 at 13:34

4 votes

Accepted

Getting minimum DFA for regular expression (11)+(111)

answered Jan 20, 2015 at 18:42

4 votes

Finding a Hoare logic correctness proof for a Repeat-Until loop

answered Mar 10, 2015 at 16:38

4 votes

Accepted

Christofides algorithm: why must an MST have even number of odd-degree vertices?

answered Mar 17, 2015 at 13:47

4 votes

DFA for the language L = { $ \omega = xy \in (a,b)^*\mid |x|_a = |y|_b $ }

answered Sep 29, 2015 at 12:25

4 votes

Converting reality to Petri net

answered May 22, 2015 at 12:26

3 votes

Show that regular languages are closed under Mix operations

answered May 19, 2015 at 13:17

3 votes

An algorithm to compute a set of states that satisfy a specific CTL formula

answered Apr 24, 2015 at 13:57

3 votes

Accepted

Witness for the $EU(\phi_1,\phi_2)$ using BDDs

answered Jul 11, 2012 at 15:35

2 votes

Why is the A* search heuristic optimal even if it underestimates costs?

answered Oct 9, 2014 at 11:38

2 votes

Why do all non-empty ω-regular languages have periodic members?

answered Mar 13, 2015 at 12:25

2 votes

Is there a name for an inverted state machine?

answered Jul 3, 2015 at 13:34

2 votes

Reduction from 3SAT

answered Dec 5, 2015 at 2:27

2 votes

How can there be 10 steps in the binary search algorithm for the phone book search problem?

answered Sep 17, 2015 at 17:10

Stack Exchange Network

48 Answers

Why is the set of all regular expressions classified as context-free, instead of regular?

DFA for accepting all binary strings of form power of $n$ (not divisible by $n$) i.e. $n^k$ for given $n$

Unprovable Post correspondence problem instance

What does least fix point and greatest fix point mean in Safety games

Loop variant for a while loop that occasionally doesn't decrease?

What are the simplest examples of programs that we do not know whether they terminate?

Can we check in polynomial time if the language of a DFA is closed against Kleene star?

Term rewriting; Compute critical pairs

Regularity of unary languages with word lengths the sum of two resp. three squares

Construct Turing Machine which accepts the language $ww$

Efficiently finding $k$ smallest elements of Cartesian product

Why is GFp -> GFq false in LTL, even though GFp and GFq are false?

What can be said in general about a homomorphism between two regular languages?

What happens to uninterpreted predicates in Ackermann's reduction?

Show that some context free languages must contain more that one non-terminal

CTL* query evaluation order

Proving the loop invariant for a simple program in Hoare logic

Getting minimum DFA for regular expression (11)+(111)

Finding a Hoare logic correctness proof for a Repeat-Until loop

Christofides algorithm: why must an MST have even number of odd-degree vertices?

DFA for the language L = { $ \omega = xy \in (a,b)^*\mid |x|_a = |y|_b $ }

Converting reality to Petri net

Show that regular languages are closed under Mix operations

An algorithm to compute a set of states that satisfy a specific CTL formula

Witness for the $EU(\phi_1,\phi_2)$ using BDDs

Why is the A* search heuristic optimal even if it underestimates costs?

Why do all non-empty ω-regular languages have periodic members?

Is there a name for an inverted state machine?

Reduction from 3SAT

How can there be 10 steps in the binary search algorithm for the phone book search problem?