AoC 2017 D3P2

local created = {['0,0']=1,['1,0']=1}
local target = 368078

local Direction = 'U'
local Directions = {['U']={0,-1},['D']={0,1},['L']={-1,0},['R']={1,0}}
local Coordinate = {1,0}
local len = 1
Part.Create(0, 0, 1, workspace, true)
Part.Create(1, 0, 1, workspace, true)

function getSurroundings()
    local x,y = Coordinate[1], Coordinate[2]
    local function c(y,x)
        return created[x .. ',' .. y]
    end
    return {c(y-1,x), c(y+1,x), c(y-1,x-1), c(y-1,x+1), c(y+1,x+1), c(y+1,x-1), c(y,x-1), c(y,x+1)}
end

function getNum(surroundings)
    local num = 0
    for _,v in pairs(surroundings) do
        num = num + v
    end
    num = (num == 0 and 1 or num)
    return num
end

for _ = 1,20 do
    for i = 1,len do
        local dir = Directions[Direction]
        Coordinate[1] = Coordinate[1] + dir[1]
        Coordinate[2] = Coordinate[2] + dir[2]
        local surroundings = getSurroundings()
        local num = getNum(surroundings)
        created[Coordinate[1]..','..Coordinate[2]] = num
        Part.Create(Coordinate[1], Coordinate[2], num, workspace, true)
        if num > target then
            print(num)
            return
        end
    end
    Direction = (Direction=='R' and 'U' or Direction == 'U' and 'L' or Direction == 'L' and 'D' or Direction == 'D' and 'R')
    len = len + (Direction=='D' and 0 or Direction == 'U' and 0 or 1)
end