regular expression for bit strings with even number of 1s

Posted by equilibrium on Stack Overflow See other posts from Stack Overflow or by equilibrium
Published on 2010-04-24T05:18:10Z Indexed on 2010/04/24 5:23 UTC
Read the original article Hit count: 164

Filed under:

homework

|

grammar

|

compiler

|

regex

Let L= { w in (0+1)* | w has even number of 1s}, i.e. L is the set of all bit strings with even number of 1s. Which one of the regular expressions below represents L?

A) (0*10*1)*
B) 0*(10*10*)*
C) 0*(10*1)* 0*
D) 0*1(10*1)* 10*

According to me option D is never correct because it does not represent the bit string with zero 1s. But what about the other options? We are concerned about the number of 1s(even or not) not the number of zeros doesn't matter.

Then which is the correct option and why?

© Stack Overflow or respective owner

Related posts about homework

parsing a list and producing a structure of that

as seen on Stack Overflow - Search for 'Stack Overflow'
;; structure representing homework points ;; nr: number - the number of the homework ;; points: number - the number of points reached (define-struct homework (nr points)) ;; parse-homework: (list of number pairs) -> (list of homework) ;; The procedure takes a list of number pairs and produces… >>> More
Scheme homework help

as seen on Stack Overflow - Search for 'Stack Overflow'
Okay so I have started a new language in class. We are learning Scheme and i'm not sure on how to do it. When I say learning a new language, I mean thrown a homework and told to figure it out. A couple of them have got me stumped. My first problem is: Write a Scheme function that returns true (the… >>> More
Unix [Homework]: Get a list of /home/user/ directories in /etc/passwd

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm very new to Unix, and currently taking a class learning the basics of the system and its commands. I'm looking for a single command line to list off all of the user home directories in alphabetical order from the /etc/passwd directory. This applies only to the home directories, and not the contents… >>> More
sequential search homework question

as seen on Stack Overflow - Search for 'Stack Overflow'
Consider a disk file containing 100 records a. How many comparisons would be required on the average to find a record using sequential search, if the record is known to be in the file? I figured out that this is 100/2 = 50. b. If the record has a 68% probability of being in the file, how many comparisons… >>> More
[Homework] Online programming editor

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, For a school project i need to write or use a online programming editor. It is a part of a bigger project. I thought of a java application, php/html/javascript or flash. I have a couple of things i could do: Find a good working application and edit it so it works with the rest of the project Find… >>> More

Related posts about grammar

Convert The Context Free Grammar to LL1 Grammar

as seen on Stack Overflow - Search for 'Stack Overflow'
hi I want to write a program to gives grammar as input and change it to LL1. my problem is converting to LL1 I don't have any algorithm to convert. I earn grammar from some input text by a simple text analyzer but how I can change it to LL1 ? is there any algorithm that is clear to implement. >>> More
English Grammar Parsing in PHP (Link Grammar)

as seen on Stack Overflow - Search for 'Stack Overflow'
Is there anyway to use the Link Grammar or AbiSource grammar checker in PHP (or C# but I'd prefer php)? I need to have a tree structure for english sentences. Any ideas? The only things I found were in C and I can't use them on a shared host. >>> More
Good grammar for date data type for recursive descent parser LL(1)

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm building a custom expression parser and evaluator for production enviroment to provide a limited DSL to the users. The parser itself as the DSL, need to be simple. The parser is going to be built in an exotic language that doesn't support dynamic expression parsing nor has any parser generator… >>> More
Parsing a string, Grammar file.

as seen on Stack Overflow - Search for 'Stack Overflow'
How would I separate the below string into its parts. What I need to separate is each < Word including the angle brackets from the rest of the string. So in the below case I would end up with several strings 1. "I have to break up with you because " 2. "< reason " (without the spaces) 3. "… >>> More
Efficient Context-Free Grammar parser, preferably Python-friendly

as seen on Stack Overflow - Search for 'Stack Overflow'
I am in need of parsing a small subset of English for one of my project, described as a context-free grammar with (1-level) feature structures (example) and I need to do it efficiently . Right now I'm using NLTK's parser which produces the right output but is very slow. For my grammar of ~450 fairly… >>> More