Switch on a tuple

Protein Translation
Protein Translation in C# 
using System;
using System.Collections.Generic;

public static class ProteinTranslation
{
    public static string[] Proteins(string strand)
    {
        var length = strand.Length;
        List<String> proteins = new List<String>();
        var endIndex = 3;
        while (endIndex <= length)
        {
            var codon = strand.Substring(endIndex - 3, 3);
            var protein = ToProtein(codon);
            switch (protein)
            {
                case "STOP":
                    return proteins.ToArray();
                default:
                    proteins.Add(protein);
                    break;
            }
            endIndex += 3;
        }
        return proteins.ToArray();
    }

    private static string ToProtein(string input) =>
        input switch
        {
            "AUG" => "Methionine",
            "UUU" => "Phenylalanine",
            "UUC" => "Phenylalanine",
            "UUA" => "Leucine",
            "UUG" => "Leucine",
            "UCU" => "Serine",
            "UCC" => "Serine",
            "UCA" => "Serine",
            "UCG" => "Serine",
            "UAU" => "Tyrosine",
            "UAC" => "Tyrosine",
            "UGU" => "Cysteine",
            "UGC" => "Cysteine",
            "UGG" => "Tryptophan",
            "UAA" => "STOP",
            "UAG" => "STOP",
            "UGA" => "STOP",
            _ => throw new Exception("Invalid sequence")
        };
}

The Proteins() method starts by defining a List and a couple of variables to control iterating the codons.

While there are still characters left to iterate, a codon is set from a Substring() of the input strand. The matching protein for the codon is looked up from the private, static ToProteins() method. It is private because it isn't needed outside the class. It is static because it doesn't use any state from an instantiated object, so it does not need to be copied to every object, but remains with the class.

The ToProteins() uses a switch to look up and return the matching protein for the codon.

The returned protein is tested in a switch. If the codon was a STOP codon, then break is used to exit the loop. If not, then the protein is added to the List.

After the loop is finished, the List's ToArray() method is used to return an array of the matched proteins from the method.

11th Dec 2024 · Found it useful?

Other Approaches to Protein Translation in C#

Other ways our community solved this exercise
while (endIndex <= length)
{
    var codon = strand.Substring(endIndex - 3, 3);
    var protein = lookup[codon];
    switch (protein)
    {
        case "STOP":
            return proteins.ToArray();
Substring with Dictionary

Iterate Substrings with Dictionary. 

return strand
    .Select((_, i) => i)
    .Where(i => i % 3 == 0)
    .Select(i =>  proteins[strand.Substring(i, 3)])
    .TakeWhile(protein => protein != "STOP")
    .ToArray();
LINQ with Dictionary

Use LINQ with Dictionary. 

public static string[] Proteins(string strand) =>
    strand.Chunked(3).Select(codon => proteins[codon]).TakeWhile(protein => protein != "STOP").ToArray();

private static IEnumerable<string> Chunked(this string input, int size)
{
    for (var i = 0; i < input.Length; i += size)
        yield return input[i..(i + size)];
}
yield with Dictionary

Iterate using yield with Dictionary. 

public static string[] Proteins(string strand) =>
   strand.Chunked(3).Select(ToProtein).TakeWhile(protein => protein != "STOP").ToArray();

private static IEnumerable<string> Chunked(this string input, int size)
{
    for (var i = 0; i < input.Length; i += size)
        yield return input[i .. (i + size)];
}
yield with switch

Iterate using yield with switch.