Discussion on: Daily Challenge #175 - Complementary DNA

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PHP:

function dnaStrand(string $dnaString)
{
    $symbols = str_split($dnaString);

    $complementaryString = '';
    foreach ($symbols as $symbol) {
        switch ($symbol) {
            case 'A':
                $complementaryString .= 'T';
                break;
            case 'T':
                $complementaryString .= 'A';
                break;  
            case 'C':
                $complementaryString .= 'G';
                break;
            case 'G':
                $complementaryString .= 'C';
                break;
            default:
                return "Is '" . $symbol ."' really in your DNA?";
        }
    }

    return $complementaryString;
}

There is always a better solution, suggest one please - I'm here to learn more .)

Klára Neumannová • Jan 29 '20

OK, I found another one for PHP (7.2 and higher):

function dnaStrand(string $dnaString)
{
    $translateTable = ['A' => 'T', 'T' => 'A', 'C' => 'G', 'G' => 'C'];

    $symbols = str_split($dnaString);

    $complementaryString = '';
    foreach ($symbols as $symbol) {
        $complementaryString .= $translateTable[$symbol] ?? '';
    }

    return $complementaryString;
}