Pytographic ordering algorithm

pyto.jl

using Test

# Reference pattern for N = 13; should be able to generalize pattern to any int N
index1=[
1,1,1,1,1,1,1,1,1,1,1,1,1,2,3,4,5,6,7,8,9,10,11,12,13,13,13,13,13,13,13,13,13,
13,13,13,13,12,11,10,9,8,7,6,5,4,3,2,2,2,2,2,2,2,2,2,2,2,2,3,4,5,6,7,8,9,10,11,
12,12,12,12,12,12,12,12,12,12,12,11,10,9,8,7,6,5,4,3,3,3,3,3,3,3,3,3,3,4,5,6,7,
8,9,10,11,11,11,11,11,11,11,11,11,10,9,8,7,6,5,4,4,4,4,4,4,4,4,5,6,7,8,9,10,10,
10,10,10,10,10,9,8,7,6,5,5,5,5,5,5,6,7,8,9,9,9,9,9,8,7,6,6,6,6,7,8,8,8,7,7]

function pattern(N::Int64)
    nrng::Vector{Int64} = 1:N
    idx1::Vector{Int64} = ones(Int64, N^2)
    stop::Int64 = 0
    forward = true
    for i in (N-1):-1:0
        # Repeating integers
        start = stop + 1
        stop = start + i - 1
        idx1[start:stop] .= forward ? nrng[1] : nrng[end]
        # Incrementing/decrementing integers
        start = stop + 1
        stop = start + i
        idx1[start:stop] = forward ? nrng : reverse(nrng)
        nrng = forward ? nrng[2:end] : nrng[1:end-1]
        forward = !forward
    end
    return idx1
end

@test pattern(13) == index1