Code challenges that involve the use of regular expressions.
9
votes
2answers
447 views
Regex in reverse - decompose regular expressions
The Problem
I have a bunch of regular expressions that I need to use in some code, but I'm using a programming language that doesn't support regex! Luckily, I know that the test string will have a ...
4
votes
0answers
262 views
Complement a Regular Expression
Given a regular expression as input, output its complement. If the given regular expression matches a string, its complement should not match it, and the regex: (regex given)|(complement) should match ...
-1
votes
1answer
117 views
POSIX reg. exp to test the divisibility by 9
Write the shortest POSIX-form regular expression that matches only non-negative integers divisible by 9. The non-negative integer should be given in base 10.
19
votes
11answers
819 views
Cross-matching regular expressions
Your task here is to write two regular expressions, each of which matches the other one but does not match itself.
Both regular expressions should have this form:
/pattern/optional-flags
This is ...
3
votes
2answers
134 views
Reverse Regular expressions [closed]
The idea here is to write a little segment that will spit out regular expression patterns when given a string that matches them.
As you might have guessed, this will be a popularity contest, and I'll ...
3
votes
1answer
232 views
Match strings whose length is isolated prime
Isolated prime definition from Wikipedia:
An isolated prime is a prime number p such that neither p − 2 nor p + 2 is prime. In other words, p is not part of a twin prime pair. For example, 23 is ...
14
votes
4answers
877 views
Match strings whose length is a fourth power
Within the scope of this question, let us consider only strings which consist of the character x repeated arbitrary number of times.
For example:
<empty>
x
xx
xxxxxxxxxxxxxxxx
(Well, ...
13
votes
2answers
252 views
Singular or plural?
Here is a list of 30 English nouns in their singular and plural form. Your job is simply to write the shortest regular expression that matches all the nouns in one form and none in the other (easy, ...
0
votes
4answers
163 views
Regex - Match half of the strings
Okay, the challenge is that you have to write a regex that matches half of all strings.
Some rules to clarify:
For ANY string length(>0), if I permute all strings(of that length), exactly half of ...
54
votes
25answers
11k views
Shortest unmatchable regular expression
Your mission is to write the shortest valid regular expression that no string can match, empty string included.
Submissions must have this form ("literal notation"):
/pattern/optional-flags
...
1
vote
3answers
256 views
Regex for Finding Non-Radioactive Elements
Find the shortest regex that matches all non-radioactive elements and nothing else in the Periodic Table of Elements. This is the inverse of Regex for Finding Radioactive Elements
Radioactive ...
4
votes
2answers
216 views
Regex for Finding Radioactive Elements
Find the shortest regex that matches all radioactive elements and nothing else in the Periodic Table of Elements.
Radioactive Elements
...
18
votes
5answers
728 views
Regex Golf: Regions of Italy vs. States of USA
We've already got a meta-regex-golf problem as inspired by the xkcd comic
But, this regex golf looks fun, too! I want to distinguish between the states of the US and the regions of Italy. Why? ...
16
votes
4answers
3k views
Meta regex golf
In the spirit of this xkcd
Write a program that plays regex golf with arbitrary pairs of lists. The program should at least attempt to make the regex short, a program that just outputs ...
0
votes
2answers
365 views
Make a regex that matches certain binary numbers [closed]
Your task is to create a regular expression that matches most binary numbers with an even number of 0s and an odd number of 1s (e.g. "101100011").
The full criteria for the regex are:
matches 90% ...
7
votes
4answers
494 views
Generate regular expressions for matching natural numbers between `m` and `n`
The type of regular expression is PCRE.
Write a program that output a valid PCRE such that it matches all natural numbers between m and n and does not match anything else. No leading zeros are ...
1
vote
1answer
284 views
Convert Regexes
Suppose you have existing regexes you wish to compile using one of the submissions to Compile Regexes.
In as few characters as possible, write a program that:
accepts an existing regex as input, as ...
8
votes
2answers
494 views
Compile Regexes
In this task you have to write a program that reads a regular expression and generates another program that outputs whether an input string is accepted by that regular expression. The output must be a ...
6
votes
3answers
782 views
Self-matching regex
Write a non-trivial regex that matches itself.
For example, #.*$ will match a comment outside of a string in python until the end-of-line, and also matches itself in perl regex syntax.
Rules:
The ...
26
votes
3answers
7k views
Hard code golf: Regex for divisibility by 7
Matthias Goergens has a 63,993-character regex to match numbers divisible by 7, but that includes a lot of fluff: redundant parentheses, distribution (xx|xy|yx|yy rather than [xy]{2}) and other ...
3
votes
2answers
261 views
Negative Regexp
Write the shortest function that takes one string, and returns a regular expression that matches anything EXCEPT the input string, in parenthesis. Escape necessary characters like Perl quotemeta.
...
