An (on-going) comprehensive list of published/beta katas that are duplicates/should be retired/edited

[Voileexperiments]

While #1301 is being idle for a while, let's collect all the duplicates/low quality katas out there that should be retired/revamped/de-duplicated.

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Duplicates

Rot-13:
https://www.codewars.com/kata/rot13/
https://www.codewars.com/kata/rot13-1/
https://www.codewars.com/kata/rot13-2/
beta:
https://www.codewars.com/kata/hail-caesar
https://www.codewars.com/kata/caesars-cypher-2
Proposal: Drop all betas, and all but one published katas

Ceasar cipher:
https://www.codewars.com/kata/caeser-encryption
https://www.codewars.com/kata/dbftbs-djqifs
https://www.codewars.com/kata/caesar-cipher-helper
beta:
https://www.codewars.com/kata/caesar-cipher-1
https://www.codewars.com/kata/unofficial-fcc-challenge-basic-algorithm-scripting-caesars-cipher
https://www.codewars.com/kata/cryptography-caesar-cipher
https://www.codewars.com/kata/caesars-cipher
https://www.codewars.com/kata/caesars-cipher-1
https://www.codewars.com/kata/caesar-cipher
https://www.codewars.com/kata/casear-cypher
https://www.codewars.com/kata/caesar-cipher-1
Proposal: Drop all the betas, and all but one published katas

Fizzbuzz:
https://www.codewars.com/kata/fizz-buzz
https://www.codewars.com/kata/pre-fizzbuzz-workout-number-1
betas:
https://www.codewars.com/kata/tiy-fizzbuzz
https://www.codewars.com/kata/if-less-fizzbuzz-1
https://www.codewars.com/kata/fizzbuzz-4
https://www.codewars.com/kata/pre-fizzbuzz-workout-number-2
https://www.codewars.com/kata/fizz-buzz-2
https://www.codewars.com/kata/fizz-buzz-1
https://www.codewars.com/kata/your-basic-fizzbuzz-kata
Proposal: DROP ALL THE BETAS (Note that there are more of them, I just searched along "fizzbuzz" keyword. I know there are more because I've encountered more disguised ones in beta). Maybe we should only keep one of the published ones, I mean, they're pretty much the same, no? Except for the return type

Church numerals:
https://www.codewars.com/kata/church-numbers-1
https://www.codewars.com/kata/church-numbers-ii
https://www.codewars.com/kata/church-numbers
https://www.codewars.com/kata/church-numbers-add-multiply-exponents
https://www.codewars.com/kata/church-numbers-find-the-predecessor-and-subtract
Proposal: Only one of 1, 3, 4 should be kept. 2 is the most comprehensive but it's only in JS. Preferably we should have one version that covers all of 2 and are still available in most functional languages (and maaaaybe JS? But I don't think JS is a good idea for this).

Arithmetic expression parser:
https://www.codewars.com/kata/arithmetic-expressions-evaluator
https://www.codewars.com/kata/calculate-the-expression
https://www.codewars.com/kata/evaluate-mathematical-expression
https://www.codewars.com/kata/parsing-and-evaluation-of-mathematical-expressions
https://www.codewars.com/kata/calculator
https://www.codewars.com/kata/no-math-expression-evaluator
https://www.codewars.com/kata/route-calculator
beta:
https://www.codewars.com/kata/advanced-calculator
https://www.codewars.com/kata/my-bedmas-approved-calculator
Proposal: Drop all but one. We already have tons of arithmetic expression parser kata who are all pretty much the same except with a million variations. The problem is, all of them are pretty much the same and the quickest way to do them is to eval them via JS/Python/etc, and it's unstoppable this way (or you can just drop in the standard parser already available and tweak from there). They stop being interesting a long time ago.

Sudoku board validation:
https://www.codewars.com/kata/did-i-finish-my-sudoku
https://www.codewars.com/kata/sudoku-solution-validator
https://www.codewars.com/kata/validate-sudoku-with-size-nxn
Proposal: Drop 1 and 2, they have incredibly weak tests anyway and is covered by 3. 3 needs to revamped and added better tests and random tests, but that's after 500 limit is lifted.

Sudoku solver:
https://www.codewars.com/kata/hard-sudoku-solver
https://www.codewars.com/kata/hard-sudoku-solver-1
https://www.codewars.com/kata/sudoku-solver
https://www.codewars.com/kata/finish-this-mini-sudoku
https://www.codewars.com/kata/easy-sudoku (beta)
https://www.codewars.com/kata/sudoku-solver-number-1 (beta)
https://www.codewars.com/kata/sudoku-solver-number-2 (beta)
https://www.codewars.com/kata/sudoku-solver-number-3 (beta)
https://www.codewars.com/kata/sudoku-solver-number-4 (beta)
https://www.codewars.com/kata/sudoku-solver-number-5 (beta)
Proposal: Drop all of them and rewrite one that actually has good tests and random tests. Especially those betas: those 5 betas are duplicate of themselves

Fibonacci numbers:
https://www.codewars.com/kata/complete-fibonacci-series
https://www.codewars.com/kata/fibonacci-reloaded
https://www.codewars.com/kata/n-th-fibonacci
https://www.codewars.com/kata/memoized-fibonacci
https://www.codewars.com/kata/fast-fibonacci
https://www.codewars.com/kata/recursion-number-2-fibonacci
https://www.codewars.com/kata/big-fibonacci-numbers-1
betas:
https://www.codewars.com/kata/fibonacci-number
https://www.codewars.com/kata/the-fibonacci-sequence
https://www.codewars.com/kata/fibonacci-numberd
https://www.codewars.com/kata/efficient-recursive-fibonacci
Proposal: Drop all but one

Reverse fibonacci numbers:
https://www.codewars.com/kata/reverse-fibonacci-series
https://www.codewars.com/kata/the-iccanobif-sequence
Proposal: Drop all. They are pretty much the same as the fibonacci numbers katas anyway

Fibonacci number generators:
https://www.codewars.com/kata/custom-enumerators-fibonacci
https://www.codewars.com/kata/fibonacci-generator
https://www.codewars.com/kata/fibonacci-generator-function
https://www.codewars.com/kata/fibonacci-streaming
Proposal: Drop all but one

Fibonacci rectangle:
https://www.codewars.com/kata/perimeter-of-squares-in-a-rectangle
https://www.codewars.com/kata/perimeter-of-fibonacci-rectangle
Proposal: Drop the 2nd kata (okay, this was my fault, I approved it)

Sum of even fibonacci numbers:
https://www.codewars.com/kata/sum-even-fibonacci-numbers
https://www.codewars.com/kata/even-fibonacci-sum
https://www.codewars.com/kata/sumfibs
Proposal: Drop all but one

Factorial:
https://www.codewars.com/kata/recursion-number-1-factorial
https://www.codewars.com/kata/factorial-1
https://www.codewars.com/kata/factorial
https://www.codewars.com/kata/factorial-factory
https://www.codewars.com/kata/big-factorial
beta:
https://www.codewars.com/kata/factorializing-a-number
https://www.codewars.com/kata/factorial-fun
https://www.codewars.com/kata/unofficial-fcc-challenge-basic-algorithm-scripting-factorialize-a-number
Proposal: Drop all but one

Pascal triangle:
https://www.codewars.com/kata/pascals-triangle-number-2
https://www.codewars.com/kata/pascal-problem
https://www.codewars.com/kata/simple-fun-number-214-pascal-matrix
https://www.codewars.com/kata/pascals-triangle
beta:
https://www.codewars.com/kata/pascals-triangle-2
Proposal: Drop all but one. The last approved one must be dropped though because of its ridiculous requirement (all rows concatenated into one) and early kata overranking

Primality check:
https://www.codewars.com/kata/check-for-prime-numbers
https://www.codewars.com/kata/prime-numbers
https://www.codewars.com/kata/is-a-number-prime
https://www.codewars.com/kata/check-if-number-is-prime-without-loops
https://www.codewars.com/kata/is-a-prime
beta:
https://www.codewars.com/kata/is-it-prime
https://www.codewars.com/kata/is-prime-number
https://www.codewars.com/kata/check-if-a-number-is-prime

Prime counting:
beta:
https://www.codewars.com/kata/count-prime
https://www.codewars.com/kata/count-primes-easy
(Variant: n-th prime):
https://www.codewars.com/kata/prime-number-generator-intermediate-with-inputs-version
https://www.codewars.com/kata/nth-prime-number
(Variant: prime counting in an interval):
https://www.codewars.com/kata/count-primes-easy
https://www.codewars.com/kata/count-primes
https://www.codewars.com/kata/finding-a-prime-number-in-an-interval

Prime generator:
https://www.codewars.com/kata/prime-numbers
https://www.codewars.com/kata/get-n-first-prime-numbers
https://www.codewars.com/kata/simple-prime-number-generator
https://www.codewars.com/kata/array-of-all-primes-up-to-number-n
https://www.codewars.com/kata/prime-number-generator-simple-version
https://www.codewars.com/kata/array-of-primes
https://www.codewars.com/kata/first-n-prime-numbers
beta:
https://www.codewars.com/kata/prime-finder

Sum of primes:
https://www.codewars.com/kata/sum-of-primes-1
beta:
https://www.codewars.com/kata/sum-of-primes

Sieve:
https://www.codewars.com/kata/master-your-primes-sieve-with-memoization
https://www.codewars.com/kata/sieve-of-eratosthenes
beta:
https://www.codewars.com/kata/sieve-of-eratosthenes-1
Proposal: Revamp and prune all these prime katas. There are only 3 algorithms involved:

• Trial division
• Sieve
• Sometimes number-theoretic prime check (e.g Miller-Rabin)

So in some sense, all of them are boring and kind of a duplicate.

Integer factorization:
https://www.codewars.com/kata/prime-factorization
https://www.codewars.com/kata/prime-factors
https://www.codewars.com/kata/primes-in-numbers
beta:
https://www.codewars.com/kata/prime-factors-1
https://www.codewars.com/kata/prime-factorisation-in-index-notation
https://www.codewars.com/kata/prime-factorisation
https://www.codewars.com/kata/factorization-1
Proposal: Drop all but one

Trailing zeros in factorial:
https://www.codewars.com/kata/number-of-trailing-zeros-of-n
https://www.codewars.com/kata/factorial-tail
https://www.codewars.com/kata/trailing-zeros-in-factorials-in-any-given-integer-base
Proposal: Drop 2 (2 and 3 are exactly the same except 3 is slightly more performance heavy), and maybe 1 since it's a subset of 3.

Goldbach conjecture:
https://www.codewars.com/kata/goldbachs-conjecture-1
https://www.codewars.com/kata/goldbachs-conjecture-prime-numbers
https://www.codewars.com/kata/goldbachs-conjecture
Proposal: Drop all but one

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Low quality katas

Base91 encoding: https://www.codewars.com/kata/base91-encoding-and-decoding
...Okay, it was my mistake to approve this. It should really be sent back to beta/retired. (Though one has to wonder why beta testers are giving it very satisfied in the first place when the kata description is far from adequate and they're just all copying the same piece of code from the web. I was naive back then. If it was me now I'd probably have raised like 3 issues to it.)

Subtract the sum: https://www.codewars.com/kata/subtract-the-sum
Highly controversial for obvious reasons

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Broken katas

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[Unihedro]

Trailing zeros in factorial:
https://www.codewars.com/kata/number-of-trailing-zeros-of-n
https://www.codewars.com/kata/factorial-tail
https://www.codewars.com/kata/trailing-zeros-in-factorials-in-any-given-integer-base
Proposal: Drop 2 (2 and 3 are exactly the same except 3 is slightly more performance heavy), and maybe 1 since it's a subset of 3.

I disagree that 1 is a subset of 3; It covers a more narrow domain which can be modeled a lot more simply than the arbitrary base problem and is a good stepping stone for the relevant algorithms (another common task is to find largest k such that n! mod p^k == 0 where p is some prime number input, which I haven't seen, but I also haven't done many problems on codewars (please link to me if you see it)), not to mention that it has wider translation coverage (can't judge if it's better, though) which is not matched by either 2 or 3, so it's more readily available to more users to practice.

2 probably deserves the retirement though.

[Unihedro]

Proposals for treatment as low quality katas:

https://www.codewars.com/kata/text-align-justify/discuss 28 open issues nonexistent sample tests, translations are apparently even worse than the source; proposition: clean up needed

https://www.codewars.com/kata/ip-validation/discuss/ 16 open issues <- although it's not really that bad. 4kyu is vastly overrating it for current standards since it's a simple validation problem, and it's missing sample tests in CoffeeScript, Javascript etc; proposition: rewrite needed, possibly retire old kata in favour of realigning the score

https://www.codewars.com/kata/base64-encoding/discuss 18 open issues ...

[Voileexperiments]

@Unihedro those katas can be boiled down to ~3 unique issues: others are just people keep raising the same issue again without adding anything new (yes, people like to do that all the time). And the issue boils down to, unsurprisingly, broken translations. If I have time to clean up all those duplicate issues I'd probably have just fixed the translation, but I didn't do the latter, so ;-)

[docgunthrop]

The following kata can also be retired:
https://www.codewars.com/kata/regular-expression-check-if-divisible-by-0b101-5
It's an exact duplicate of:
https://www.codewars.com/kata/regular-expression-for-binary-numbers-divisible-by-5

[Blind4Basics]

Low quality kata (still in beta) to retire: https://www.codewars.com/kata/52f5f8757c461de6310001e8 (writing the sum of a and b... / 20 issues / no random tests / ...)

[Blind4Basics]

in the low quality katas to retire:

• https://www.codewars.com/kata/escape-the-mines/ (fixed tests only, and checking for an exact path instead of A shortest path)

[anter69]

https://www.codewars.com/kata/factorization/

[Voileexperiments]

https://www.codewars.com/kata/zero-fill-dot-dot-dot-for-the-queen

This is now obsolete since padStart is available from Node 8.

[dinglemouse2250]

This is now obsolete since padStart is available from Node 8.

But not all Kata are applicable for all languages. And on the other side of the coin, just because one language has a library function does not make it a bad Kata for other languages....

[Voileexperiments]

Yes, but my point there is that lots people make katas that are language-specific, and so they're not portable to most other languages and, hence, the status of other languages does not apply to the kata.

I know at least 4 published white katas that exhibits this, but we'll see.