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grid = Int.(hcat(collect.(readlines("day22.txt"))...).=='#')'
testgrid = [0 0 1; 1 0 0; 0 0 0]
rule1 = reshape([0 -1 1 0 0 1 -1 0], 2, 2, :)
rule2 = reshape([0 -1 1 0 1 0 0 1 0 1 -1 0 -1 0 0 -1], 2, 2, :)
function virus(grid, steps, dirs)
(i, j), n = div.(size(grid).+1, 2), size(dirs, 3)
di, dj, inf = -1, 0, 0
g = Dict((i,j)=>grid[i,j]*div(n,2) for i=1:size(grid,1), j=1:size(grid,2))
for _=1:steps
x = get(g, (i,j), 0)
g[i,j] = mod(x+1, n)
(di, dj) = [di dj] * dirs[:,:,x+1]
if x+1==n/2; inf+=1 end
i+=di; j+=dj
end
inf
end
part1 = virus(grid, 10^4, rule1)
part2 = virus(grid, 10^7, rule2)
println(part1)
println(part2)
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