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Posted on Jan 29, 2020

Daily Challenge #175 - Complementary DNA

#challenge

Setup

Deoxyribonucleic acid (DNA) is a chemical found in the nucleus of cells and carries the "instructions" for the development and functioning of living organisms.

In DNA strings, symbols "A" and "T" and "C" and "G" are complements of each other. Implement a function DNA_strand to match the given side of DNA with its complementary side.

Examples

DNA_strand("ATTGC") # return TAACG
DNA_strand("GTTAAC") # return CAATTG

Tests

DNA_strand("AAAA")
DNA_strand("CTACC")
DNA_strand("GTAT")

Good luck!

This challenge comes from JustyFY on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

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

Top comments (18)

Isaac Lyman • Jan 29 '20 • Edited

This sounds like a one-liner in JS. Let's see...

const DNA_strand = str => str.split('').map(l => l === 'A' ? 'T' : l === 'T' ? 'A' : l === 'G' ? 'C' : l === 'C' ? 'G' : '').join('');

As a bonus, any non-DNA letters will be ignored.

Vansh.c • Aug 3 '23

i am fresher can you tell me what does this ( => )operator do.

Your help is appreciated.

Isaac Lyman • Aug 3 '23

It’s an arrow function (or anonymous function).

function(a, b) {return a + b;}

Is (almost) the same as:

(a, b) => a + b

There are a few differences but most of the time they aren’t anything to worry about. If you care, this is a good overview: levelup.gitconnected.com/7-differe...

Jehiel Martinez • Jan 29 '20 • Edited

JS:

function DNA_strand (str) {
    let result = '';
    for(i=0; i<str.length; i++){    
        switch (str[i]) {
            case 'A':
                result = result + 'T';
                break;
            case 'T':
                result = result + 'A';
                break;
            case 'C':
                result = result + 'G';
                break;
            case 'G':
                result = result + 'C';
                break;
            default:
                return 'Your DNA is not from this planet';
        }
    }
    return result
};
```

Valts Liepiņš • Jan 29 '20

Ruby keeps on pleasantly surprising me:

def DNA_strand str
    str.tr 'ATCG', 'TAGC'
end

Valts Liepiņš • Jan 29 '20

Seems like Lua also has a neat solution:

function DNA_strand(str)
    return (str:gsub('.', {A='T',T='A',C='G',G='C'}))
end

Avalander • Jan 30 '20

Another javascript solution

const complementaryKeys = (prev, [ a, b ]) =>
  Object.assign(prev, {
    [a]: b,
    [b]: a,
  })

const pair = (...entries) => {
  const pairs = entries.reduce(complementaryKeys, {})
  return x => pairs[x] || ''
}

const dnaPairs = pair(
  [ 'A', 'T' ],
  [ 'C', 'G' ]
)

const mapStr = fn => str =>
  str.split('')
    .map(fn)
    .join('')

const dnaStrand = mapStr(dnaPairs)

Ruan Engelbrecht • Jan 29 '20

JavaScript:

const mapping = {
  A: 'T',
  T: 'A',
  C: 'G',
  G: 'C'
};

const DNA_strand = seq =>
  seq
    .split('')
    .map(x => mapping[x])
    .join('');

Kyle Jones • Jan 29 '20 • Edited

In Python:

def DNA_strand(strand):
    '''
    Returns the complementary strand of DNA for a given strand.
    '''
    complementary_strand = ""
    for symbol in strand:
        if symbol == 'A':
            complementary_strand += 'T'
            continue
        if symbol == 'T':
            complementary_strand += 'A'
            continue
        if symbol == 'C':
            complementary_strand += 'G'
            continue
        if symbol == 'G':
            complementary_strand += 'C'
            continue
    return complementary_strand


print(DNA_strand("ATTGC"))
print(DNA_strand("GTTAAC"))

Daniel Barwikowski • Jan 30 '20

private static string DNA_strand(string dna)
{
    var sb = new StringBuilder();
    var bytes = Encoding.ASCII.GetBytes(dna);
    foreach (var b in bytes)
    {
        if ((b & 0b0000_0010) == 0)
        {
            sb.Append((char) (b ^ 0b0001_0101));
        }
        else
        {
            sb.Append((char) (b ^ 0b0000_0100));
        }
    }

    return sb.ToString();
}

Daniel Barwikowski • Jan 30 '20 • Edited

A   100 0001
T   101 0100

C   100 0011
G   100 0111

---- -|-- - this bit always changes

---| ---| - this bits only changes when ---- --|- is set to 0

Craig McIlwrath • Jan 29 '20 • Edited

Haskell:

complement :: Char -> Either String Char
complement 'A' = Right 'T'
complement 'T' = Right 'A' 
complement 'C' = Right 'G' 
complement 'G' = Right 'C' 
complement c = Left $ "invalid nucleic acid " ++ [c]

dnaStrand :: String -> Either String String 
dnaStrand = sequence . map complement

Returns a Left value if there is a character other than AGTC

kesprit • Jan 30 '20

Swift solution :

func dnaStand(dna: String) -> String {
    let dnaMatching: [Character:Character] = ["A":"T","T":"A","C":"G","G":"C"]
    return dna.reduce(into: "") { $0.append(dnaMatching[$1] ?? "" as! Character) }
}


dnaStand(dna:"ATTGC")
dnaStand(dna:"GTTAAC")
dnaStand(dna:"AAAA")
dnaStand(dna:"CTACC")
dnaStand(dna:"GTAT")

Ryan Beckett • Jan 29 '20 • Edited

Swift:


func DNA_strand( _ dna: String) -> String {
  let swapTable = [("A", "T"), ("T", "A"), ("C", "G"), ("G", "C")]

  return dna.map { char in
    swapTable.map { (key, value) in
      String(char) == key ? value as String : ""
    }.joined()
  }.joined()

}

I'm trying to complete these everyday for 30 days (hopefully more) - feedback more that welcome here please, thank you! Github PR

View full discussion (18 comments)

DEV Community

Daily Challenge #175 - Complementary DNA

Setup

Examples

Tests

Top comments (18)

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