AoC 20 Trench Map

aco20.jl

lines = readlines("input20.txt")
algo = lines[1]|> x->[c=='.' ? false : true for c in x]
imag = lines[3:end] .|> (x->[c=='.' ? false : true for c in x]) |> x->hcat(x...)

# pad the image by zeroes to simulate the infnitued 
function pad(imag,pad)
    oldsize = size(imag)
    newsize =  oldsize .+ 2*pad
    new_imag = zeros(eltype(imag), newsize...)
    new_imag[pad+1:oldsize[1]+pad,pad+1:oldsize[2]+pad] .= imag
    new_imag
end

function outside(pos, Ifirst, Ilast )
    (any(pos.I .< Ifirst.I) || any(pos.I .> Ilast.I)) && return true
    false
end

function enhance(imag,algo, background=0)
    out = similar(imag)
    R = CartesianIndices(imag)
    Ifirst, Ilast = first(R), last(R)
    I1 = oneunit(Ifirst)
    for pos in R
        n = 0 % UInt16
        for element in pos-I1:pos+I1
            if outside(element,  Ifirst, Ilast )
               n = (n<<1) + (background%UInt16)
            else
               n = (n<<1) + (imag[element]%UInt16) 
            end
        end
        n += 1
        out[pos] = algo[n]
    end
    out
end

# Part 1 
padded_imag = pad(imag,2) 
out = enhance(padded_imag ,algo)
out = enhance(out,algo, 1)
println("Part one: $(sum(out))")
# Now for part 2 
out =  pad(imag,50)
for i=1:50
    out = enhance(out,algo, (i-1)%2)
end
println("Part two: $(sum(out))")