eu300.rb

L=11
@field = Array.new(32*32) {0}
@vecs = [[1,0], [0,-1], [-1,0], [0,1]]

def fld(x,y) @field[y*32+x] end
def set(x,y,v) @field[y*32+x] = v end
def step(x, y, ang) 
    vx,vy = @vecs[ang & 3]
    return x+vx, y+vy
end

@dna = Array.new(L)
@path = Array.new(L) {[16,16]}

def cpn
    n = 0
    for p in @path do
        if fld(p[0], p[1])==1 then
            n += 1 if fld(p[0]+1, p[1])==1
            n += 1 if fld(p[0], p[1]+1)==1
        end
    end
    n
end

def draw(n, x,y, angle)
    return if fld(x,y) != 0
    set(x,y, @dna[n])
    @path[n][0] = x; @path[n][1] = y
    if n == L-1 then
        cp = cpn()
        @maxcpn = cp if cp > @maxcpn
        set(x,y, 0)
        return
    end
    nx,ny = step(x,y, angle)
    draw(n+1, nx,ny, angle)
    nx,ny = step(x,y, angle-1)
    draw(n+1, nx,ny, (angle-1)&3)
    nx,ny = step(x,y, angle+1)
    draw(n+1, nx,ny, (angle+1)&3)
    set(x,y, 0)
end

def optLen(seed)
    for i in (0...L) do
        @dna[i] = if (seed & (1 << i)) > 0 then 2 else 1 end 
    end
    set(16,16, @dna[0])
    @maxcpn = 0
    draw(1, 17,16, 0)
    @maxcpn
end

puts (0...(1<<L)).map{|i| optLen(i)}.reduce(:+)