Can you solve this puzzle involving regular expressions?

AI Thread Summary
The discussion revolves around a challenging regular expressions puzzle from a BAE Systems interview. Participants are attempting to match specific regex patterns to form coherent sentences, with a focus on the phrase "It's not just security, it's defence." There are difficulties with the second line of regex, which requires precise placement of 's' characters and spaces, leading to confusion about the expected output. The spelling of "defence" is noted as a potential stumbling block for non-British applicants, reflecting the company's origins. Overall, the puzzle highlights the complexities of regex and its application in cybersecurity contexts.
MesonMarcus
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can anyone help solve this puzzle regarding regular expressions? I was given this in an interview test from BAE systems cyber security department a few years ago and just came across it again, still haven't managed to get anywhere like an answer. I have tried matching each line of regex to form words but no look. The puzzle is as follows:
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.{14}security.{15}
[^s]{3}s [^s]{6}s[^s] s[^s]{12}s [^s]{8}
def
^It'..[ywkni][klmop][zwta]
ce.$
jus
[^f]*fenc
y, it's
t ...t

Give your answer.

This is the best I could get...

...security...
bees xxxxxxsx sxxxxxxxxxxxxs xxxxxxxx
def
It's not
ce.
jus
xfenc
y, it's
t xxxt

but makes no sense...
 
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The idea is to find a line that matches each of the regex strings.

[^x] means doesn’t match x and

{99} is the number of times to match with * for 0 or more and + for one or more.

^ outside of the [ ] means beginning of the string and $ means the end of the string.

I think the first line matches a string containing the text security

. . . . . . . . . . . . . . s e c u r i t y . . . . . . . . . . . . . . .

the second line matches a line where the 4th character is an s and some more s later on.

I t ‘ s . n o t . . . . . . s e c u r i t y . . . . . . . . . . . . c e .

my attempt yielded the sentence but it doesn’t match all the criteria.

I T ' S _ N O T _ J U S T _ S E C U R I T Y , _ I T ' S _ D E F E N C E .
 
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Likes pbuk
awesome!
 
jedishrfu said:
I T ' S _ N O T _ J U S T _ S E C U R I T Y , _ I T ' S _ D E F E N C E .
It's not just security, it's defence. works for me.
 
I had trouble with line 2 aka the s not s expression. It seemed not all the ‘s’ characters lined up in my solution although I didn’t test it.

I ll have to try it in AWK, my favorite go to language.
 
jedishrfu said:
I had trouble with line 2 aka the s not s expression. It seemed not all the ‘s’ characters lined up in my solution although I didn’t test it.
Line 2 only depends on 's's and spaces in the right place. It won't match if you use the US spelling for defence, unsurprisingly given the employer :biggrin:
 
But it seemed solving it on paper that a couple of s characters were off According to that regex. I chalked it up to the possibility that the expression was an outlier perhaps designed to be misleading ala obfuscation Aka security thru obscurity.

I as puzzled by the defence spelling too but decided that since BAE is a British company that the spelling was correct. I imagine that would have tripped up a few Americans applying for the job. :-)
 
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