Daily Challenge #103 - Simple Symbols

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Daily Challenge (120 Part Series)

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(or not...) 77) Daily Challenge #77 - Bird Mountain 78) Daily Challenge #78 - Number of Proper Fractions with Denominator d 79) Daily Challenge #79 - Connect Four 80) Daily Challenge #80 - Longest Vowel Change 81) Daily Challenge #81 - Even or Odd 82) Daily Challenge #82 - English Beggars 83) Daily Challenge #83 - Deodorant Evaporator 84) Daily Challenge #84 - Third Angle of a Triangle 85) Daily Challenge #85 - Unwanted Dollars 86) Daily Challenge #86 - Wouldn't, not Would. 87) Daily Challenge #87 - Pony Express 88) Daily Challenge #88 - Recursive Ninjas 89) Daily Challenge #89 - Extract domain name from URL 90) Daily Challenge #90 - One Step at a Time 91) Daily Challenge #91 - Bananas 92) Daily Challenge #92 - Boggle Board 93) Daily Challenge #93 - Range Extraction 94) Daily Challenge #94 - Last Digit 95) Daily Challenge #95 - CamelCase Method 96) Daily Challenge #96 - Easter Egg Crush Test 97) Daily Challenge #97 - Greed is Good 98) Daily Challenge #98 - Make a Spiral 99) Daily Challenge #99 - Balance the Scales 100) Daily Challenge #100 - Round Up 101) Daily Challenge #101 - Parentheses Generator 102) Daily Challenge #102 - Pentabonacci 103) Daily Challenge #103 - Simple Symbols 104) Daily Challenge #104 - Matrixify 105) Daily Challenge #105 - High-Sum Matrix Drop 106) Daily Challenge #106 - Average Fuel Consumption 107) Daily Challenge #107 - Escape the Mines 108) Daily Challenge #108 - Find the Counterfeit Coin 109) Daily Challenge #109 - Decorate with Wallpaper 110) Daily Challenge #110 - Love VS. 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Write a function that will take a string and determine if it is an acceptable sequence. The string will be composed of + and = symbols with several characters between them. For the string to be acceptable, each character must be surrounded by + symbols.

Examples:
(++d+===+c++==a) => false, because a is not surrounded by +.
(+d+e+===+q+=) => true, because all characters are surrounded by +.

Test cases:
"f++d+"
"++q++qq=z"
"==++z+=+q+"

Want to propose a challenge idea for a future post? Email yo+challenge@dev.to with your suggestions!

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simple Haskell solution:

verify :: String -> Bool
verify [] = True
verify ('+':x:'+':xs)
    | isLetter x = verify $ '+':xs
verify (x:xs)
    | isLetter x = False
    | otherwise = verify xs
 

I took your solution and simplified it:

verify :: String -> Bool
verify [] = True
verify ('+':x:'+':xs) = verify $ '+':xs
verify ('+':xs) = verify xs
verify ('=':xs) = verify xs
verify (_) = False

Also note that nothing in the question indicates the characters other than = and + can only be letters. Your version would accept 1 even though 1 is a character and it is not surrounded by +s.

 

This solution assumes that the only other character is =. No idea if you can assume this

The string will be composed of + and = symbols with several characters between them.

If I'm reading this correctly, it means that the characters are categorized into three categories:

  1. +
  2. =
  3. Other

So any character other than + and = must be surrounded by +s - which is exactly what my version checks.

 

Whoa, I was comming with something that involved using an indexedMap but your solution is very clever. Thanks for sharing your awesome answer!

Also, isn't isLetter part of Data.Char? Or no need to import that to use the isLetter function?

 

yes, that function is from Data.Char, I omitted the import together with the module header.

 

I've never been the best with Regex, but here's a possible attempt:

JavaScript

const acceptableSequence = str => !/(?<!\+)\w|\w(?!\+)/.test(str);

EDIT: Misread the requirements, don't need to account for end and beginning of line characters as exceptions.

 

\w generally includes the underscore, which is why I used the explicit character class.

 

That's a good point. I figured I'd use \w since nothing in the challenge indicated that the characters need be only alphabetical, but obviously you could just as easily sub in [a-zA-Z] or whatever fits the use case.

I interpreted “The string will be composed of + and = symbols with several characters between them.” as only +, = and letters. 😀

That definitely makes the most sense, given the examples. I really appreciate you reaching out to clarify - definitely want to make sure I'm accurately hitting objectives.

I'm just assuming either, but at least this is turning into a good lesson on how requirements get confused between whoever plans them and developers 😉

 

Javascript:

acceptable = str => [...str].every((x, i, a) => x == '+' || x == '=' || (a[i - 1] == '+' && a[i + 1] == '+'))
 

Ruby:

def verify(s)
  s !~ /(?<!\+)[a-z]|[a-z](?!\+)/
end

verify "f++d+"
#=> false

verify "++q++qq=z"
#=> false

verify "==++z+=+q+"
#=> true
 

Here's an alternative version in Raku (formerly Perl6), which IMHO is more readable due to the more expressive lookaround assertions:

sub verify { @_ !~~ /<!after \+><[a..z]>|<[a..z]><!before \+>/ }

verify "f++d+"
# False
verify "++q++qq=z"
# False
verify "==++z+=+q+"
# True
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