Questions tagged [regular-expression]
Code challenges that involve the use of regular expressions.
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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:
...
32
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answers
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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 ...
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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 ...
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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 ...
- 71.2k
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answer
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Regex that only matches itself
There are some pretty cool challenges out there involving regex (Self-matching regex, Regex validating regex)
This may well be impossible, but is there a regex that will ONLY match itself?
NOTE, ...
- 3,731
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Tips for Regex Golf
Similar to our threads for language-specific golfing tips: what are general tricks to shorten regular expressions?
I can see three uses of regex when it comes to golfing: classic regex golf ("here ...
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votes
5
answers
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Adding Numbers with Regex
I want to try a new type of regex golf challenge, which asks you to solve nontrivial computational tasks with nothing but regex substitution. To make this more possible and less of a chore, you will ...
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answers
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Debunking Stroustrup's debunking of the myth “C++ is for large, complicated, programs only” [closed]
Stroustrup has recently posted a series of posts debunking popular myths about C++. The fifth myth is: “C++ is for large, complicated, programs only”. To debunk it, he wrote a simple C++ program ...
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Hard code golf: Regex for divisibility by 7
Matthias Goergens has a 25,604-character (down from the original 63,993-character) regex to match numbers divisible by 7, but that includes a lot of fluff: redundant parentheses, distribution (...
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votes
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answers
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Cops and Robbers: Reverse Regex Golf
Note: This challenge is now closed. Any future cops' submission will not be considered for the accepted answer. This is to ensure that no one can post a very simple regex in the future that only ...
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votes
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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"):
...
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Cops: Make a regex - Make a snake
This is the cop's thread. The robber's thread is here.
Write a code that takes an input n and creates a n-by-n "snake matrix".
A snake matrix is a matrix that ...
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Interpret /// (pronounced 'slashes')
Because we can't get enough of esoteric language golfs, can we?
///—pronounced slashes—is a fun little language based on the s/// regex-replacement ...
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16
votes
4
answers
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Match the Stack Exchange URLs
Prologue
After installing an anti-XSS browser extension, Stack Snippets suddenly stopped working all across the Stack Exchange network. I could no longer learn from Stack Overflow, see working demos ...
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A Different Kind of Meta Regex Golf
Notice: Following popular demand I have slightly relaxed the rules:
The maximum regex size grows by 1 byte every 5 answers. Answer N may use up to 29 + ⌈N/5⌉ bytes.
The score of each answer ...
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votes
3
answers
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HexaRegex: A Tribute to Martin Ender
Martin Ender recently hit 100K, and has come up with some pretty awesome languages. We're going to have a bit of fun with one of them, Hexagony (and a bit of regex for Retina)
As a brief overview, ...
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Complement a POSIX Extended Regular Expression
Given a POSIX Extended Regular Expression as input, output its complement (also a POSIX ERE). If the given regular expression matches a string, its complement should not match it, and the regex: ...
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Gotta Match Them All! Write a regex to match the original 151 Pokemon but no subsequent Pokemon
The original 151 Pokemon, in an array format suitable for initializers:
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votes
2
answers
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Partial Ordering of Regex Patterns
For the purpose of this challenge, we say that a regex pattern matches a string if the entire string is matched by the pattern, not just a substring.
Given two regex patterns A and B, we say that A ...
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votes
41
answers
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Robbers: Crack the regex - Make a snake
This is the robber's thread. The cop's thread is here.
A snake matrix is a square matrix that follows this pattern:
3-by-3:
1 2 3
6 5 4
7 8 9
and 4-by-4:
...
- 45.7k
22
votes
13
answers
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Check if simple regex matches string
A simple regex is either:
_ (which matches the empty string)
Any lowercase letter a to z (...
user84442
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votes
11
answers
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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:
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answers
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Remove single line and multiline comments from string
Goal
Using the programming language of your choice, write the shortest program to eliminate comments from a string representing a C program.
Input
The string can be taken as any form of input, but ...
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votes
2
answers
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Complement of a Regex
For the purposes of this challenge, we define a postfix regex dialect with alphabet {1, 0} and the following operations:
1 and <...
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votes
9
answers
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Sum the time durations
Challenge
Write the shortest code that can sum all the time durations that appear in the stdin. The program must only consider the strings that match with one of the following patterns and ignore the ...
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votes
2
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ValiDate ISO 8601 by RX
Challenge
Find the shortest regex that
validates, i.e. matches, every possible date in the Proleptic Gregorian calendar (which also applies to all dates before its first adoption in 1582) and
does ...
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3
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Self-matching regex [closed]
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 ...
- 261
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votes
4
answers
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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
...
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votes
6
answers
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The greedy regex (cops)
This is the cops' post. The robbers' is here.
You make a program and a regex.
For most inputs, one of the following happens:
the regex doesn't match, and the program returns a falsey value
the ...
user58826
7
votes
1
answer
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Regular expression parser
This task is a classic programming task: Implement a regular expression parser. That is, write a program or function which takes a string describing a regular expression and a candidate string, and ...
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4
answers
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Count regex matches
Your task
Given a simple regular expression, you have to count how many strings of length n have a match of length n with the ...
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answers
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Negative Regexp [closed]
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 ...
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4
votes
4
answers
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The greedy regex (robbers)
This is the robbers' post. The cops' is here.
Your challenge is to take a cop's post and find an input that the regex matches but the program returns a falsey value.
Once you have cracked a cop's ...
user58826