
World’s longest palindrome? - rmeertens
http://www.pinchofintelligence.com/worlds-longest-palindrome/
======
AndrewOMartin
"A man, a plan, a canoe, pasta, heros, rajahs, a coloratura, maps, snipe,
percale, macaroni, a gag, a banana bag, a tan, a tag, a banana bag again (or a
camel), a crepe, pins, Spam, a rut, a Rolo, cash, a jar, sore hats, a peon, a
canal-- Panama!" \- Guy Steele, CLTL2

~~~
DonaldFisk
Some years after the faked death of John Darwin, who disappeared after rowing
out to sea in his canoe, and was planning to start a new life with his wife in
Panama with the insurance payout, the Grauniad had the headline "A man. A
plan. A canoe. Panama" in an article
([https://www.theguardian.com/uk/2008/jul/23/canoe.ukcrime1](https://www.theguardian.com/uk/2008/jul/23/canoe.ukcrime1))
about the case.

~~~
AndrewOMartin
He could have at least had the good decency to have used a KayaK.

~~~
thorin
Pretty sure it was a kayak. People in the UK are very confused by the
difference. E.g. British Canoe Union largely supports kayaking. I tend to use
the terms interchangeably having been an active kayaker for around 25 years.
The British public really struggle with the difference.

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asimjalis
See banana, banana, banana, banana, banana, banana, banana, banana, banana,
banana, banana, banana, banana, banana, banana, banana, banana, banana,
banana, banana, banana, banana, banana, banana, banana, banana, banana,
banana, banana, banana, banana, banana, bees.

For any N "See [banana,]* bees." can be longer than N.

------
sp332
"Dammit, I'm mad..." [https://quotereference.wordpress.com/2014/12/11/dammit-
im-ma...](https://quotereference.wordpress.com/2014/12/11/dammit-im-mad/)

PS I converted this into three palindromic tweets
[https://twitter.com/sep332/status/928484353310711808](https://twitter.com/sep332/status/928484353310711808)

------
marzell
How does this count as a palindrome? It's just a bunch of nonsense words
(ignoring all the acronyms, are the rest all actually even really words?)
separated by commas, that doesn't even seem to pretend to take on the
structure of a sentence.

Am I misunderstanding the level of coherence of the text? If the requirements
are that loose, it seems it would be trivial to generate a 'palindrome' of
arbitrary length.

~~~
xamuel
Think of it like an ad slogan.

"A man, a plan, a canal-- [you should book a trip to] Panama[, a country whose
history is summed up by this witty list of things]!"

What I'd like to see is a version where instead of optimizing just for length,
the palindrome is optimized for noun-phrases that genuinely have legit
connections to Panama (as the brilliant original, "a plan, a man, a canal",
does).

~~~
marzell
Apologies, I was actually referring to the very large (6MB!) palindrome text
file [0] provided if you follow the article link to the GitHub project [1]. I
guess the palindrome of discussion in this link is somewhat ambiguous, because
there's not one specific palindrome that the article refers to.

[0]
[https://raw.githubusercontent.com/rmeertens/palindromes/mast...](https://raw.githubusercontent.com/rmeertens/palindromes/master/longest_palindrome.txt)
[1]
[https://github.com/rmeertens/palindromes](https://github.com/rmeertens/palindromes)

~~~
xamuel
It's the same thing. "A man, a plan, (6MB worth of other junk)-- Panama!"

It's questionable what that other junk has to do with Panama. But
grammatically, the structure is the same.

------
kiliankoe
I was recently dumbfounded by the fact that

    
    
        ()() 
    

is not a palindrome, but

    
    
        ())(
    

is. It's obvious, sure, but it still doesn't look right.

~~~
luizfzs
It's not obvious for me (maybe you are joking and I didn't get it)

~~~
kiliankoe
Try substituting other symbols, which makes it easier to see. 1 for ( and 0
for ) for example.

Then we have

    
    
        1010
    

and

    
    
        1001

~~~
luizfzs
_mindblow_

------
DonaldFisk
The longest palindrome has infinite length. Start with any palindrome, e.g.
"radar". You can make a new palindrome: "radar, sides reversed, is radar".
That can then be used to create the palindrome "radar, sides reversed, is
radar, sides reversed, is radar, sides reversed, is radar".

You can repeat this indefinitely.

------
techbio
"Never odd or even" is one some here might like to see, and perhaps suggests
the shorter palindrome, "NaN".

------
chipuni
World's shortest palindrome:

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lazycouchpotato
There's a link which takes you to the list of palindrome dates mentioned on
the website [1]. There's 38 of them, but they all take the MM/DD/YYYY format
into consideration. I wonder how much of a difference it would be by taking
DD/MM/YYYY instead.

[1] [https://www.livescience.com/33583-palindrome-dates-21st-
cent...](https://www.livescience.com/33583-palindrome-dates-21st-century-
weird.html)

~~~
interfixus
Or YYYY-MM-DD as a few of us obsessive smallendians keep insisting.

~~~
lazycouchpotato
Heh, they'd just be the reverse of DD-MM-YYYY :)

But yes, YYYY-MM-DD all the way. It's indispensable to me when sorting file
names by date.

------
fnayr
Different word trivia that I find fascinating that I feel HNers will also
appreciate:

(twelve plus one) is an anagram of (eleven plus two)

I guess that should be called a mathagram?

------
SippinLean
I was a fan of this palindromic short story (also in honor of the year 2002):
[http://spinelessbooks.com/2002/palindrome/](http://spinelessbooks.com/2002/palindrome/)

------
nathell
Here's a handcrafted one in Polish, 33K+ characters:
[http://www.palindromy.pl/pal_naj.php](http://www.palindromy.pl/pal_naj.php)

------
nathell
I'm also reminded of this IOCCC entry:
[https://www.ioccc.org/1987/westley/westley.c](https://www.ioccc.org/1987/westley/westley.c).
Strictly speaking, it's not composed of palindromes because of the mirror-
image brackets and slashes, but still, impressive.

------
type_enthusiast
I have to point out Weird Al's "Bob":
[https://www.youtube.com/watch?v=JUQDzj6R3p4](https://www.youtube.com/watch?v=JUQDzj6R3p4)

It's not a palindrome, but is a semi-sensical song masterfully composed
entirely out of palindromes (which also does a great job poking fun at Bob
Dylan).

------
jacquesm
This one is a valid sentence in Dutch:

"Nelli plaatst op n parterretrap n pot staalpillen."

The 'n's are a bit of an issue though, 'n in dutch means 'een', but reversed
that doesn't work so the 'e's got dropped and replaced by "'" but they move
from one side of the n's to the other in the reversal.

------
User23
We used find the longest palindrome in a string as an interview question at
Amazon back in 2004

~~~
alexthehurst
Did you require a certain time complexity? I came across this on Leetcode. I
found it really trivial to implement the “test all substrings” algorithm, but
fiendishly difficult to implement the “expand around centers” algorithm.

~~~
fjsolwmv
That's why trick puzzle questions are bad interview questions. Some people
have read the centers algorithm

~~~
User23
It’s not a trick question. It’s just writing a loop any CS graduate or
equivalent autodidact should have absolutely no problem with.

We didn’t require any specific time or space complexity. If the candidate
whipped out a suboptimal solution quickly and correctly and time permitted we
might ask them about that though and how it might be improved. The purpose of
the question is not to see if the candidate has memorized the answer or sees a
trick, it’s so they can demonstrate basic proficiency and systematic
reasoning.

------
psalminen
Hug of death?

~~~
myroon5
[https://web.archive.org/web/20180809171552/http://www.pincho...](https://web.archive.org/web/20180809171552/http://www.pinchofintelligence.com/worlds-
longest-palindrome/)

~~~
psalminen
Thank you. Don't know why I'm being downvoted for asking.

~~~
68c12c16
perhaps someone took it too literal and thought, _htaed fo guh != hug of
death_

I upvoted your comment to make it up for you...hope you have a good one...

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etiennemarcel
Georges Perec in 1969:
[http://homepage.urbanet.ch/cruci.com/lexique/palindrome.htm](http://homepage.urbanet.ch/cruci.com/lexique/palindrome.htm)
(1247 words)

~~~
fjsolwmv
Perec also wrote a book with no letter E, a mystery about the missing letter.
The English translation is called _A Void_. It's hard to make sense in parts,
largely works.

At parts it discusses the mysterious missing letter (E is not know) like
threeve, the integer between 3 and 4.

------
luizfzs
8102018 is not a palindromic because it isn't a valid format date (it is, but
is nonsense, so not valid on my standards :).

examples of valid date formats are: yyyy-mm-dd dd-mm-yyyy

------
evilolive
engage le jeu que je le gagne

------
Aardwolf
For single words, in Dutch there is:

koortsmeetsysteemstrook

~~~
nathell
And Finnish has saippuakivikauppias.

------
elwell
Go hang a salami, I'm a lasagna hog.

~~~
hcs
So many dynamos

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LearnerHerzog
I thought the point of palindromes were that they

1: Are the same forwards and backwards

2: Make coherent sense

Still pretty cool nonetheless, I suppose

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imtringued
This palindrome is surprisingly disappointing. Almost every word appears 100s
of times...

------
lowercased
My 2 "go to" palindromes...

I know a fat man called Ella C Namtafawnoki.

I got hang of fog nah togi.

~~~
quickthrower2
My two go to palindromes are Mr Merasemordnilapotogowtym!

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quickthrower2
Whats with Sadick? (15 times!). Also the F __*, C and S words!

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mkstowegnv
For a line level palindrome homage to Douglas Hofstadter's Crab Canon see

[https://juliagalef.com/2017/02/21/a-poem-for-douglas-
hofstad...](https://juliagalef.com/2017/02/21/a-poem-for-douglas-hofstadter/)

------
ehonda
wo nemo toss a lasso to me now!

------
white-flame
Rotavator

~~~
quickthrower2
Ada

~~~
Aardwolf
I

~~~
gebeeson
Yo banana boy

Racecar

