Complementing a Strand of DNA

Problem definition

In DNA strings, sysmbols ‘A’ and ‘T’ are complements of each other, as are ‘C’ and ‘G’.

The reverse complement of a DNA string \(s\) is the string \(s^C\) formed by reversing the symbols of \(s\), then taking the complement of each symbol (e.g., the reverse complement of ‘GTCA’ is ‘TGAC’).

Given

A DNA string \(s\) of length at most 1000 base pairs.

Return

The reverse complement \(s^C\) of \(s\).

Sample dataset

AAAACCCGGT

Sample Output

ACCGGGTTTT

Solution

function reverse_complement(s::AbstractString)
    rev_map = Dict{Char, Char}(
        'A' => 'T', 'T' => 'A',
        'G' => 'C', 'C' => 'G'
    )
    io = IOBuffer()
    for char in reverse(s)
        write(io, rev_map[char])
    end
    return String(take!(io))
end

function main()
    first_line = readline(ARGS[1])
    output = reverse_complement(first_line)
    write("output.txt", output)
    println(output)
end

main()