I’m not sure I understand why you expand the universe twice and then take sum of each expanded universe distances and then divide by two. Why not just expand the universe once and sum the manhattan distances of the galaxies once?
stevensonmt
Aetherus
I only expanded the universe once for each part of the puzzle. Dividing by two is because for each pair of the galaxies a and b, I calculated the distance between a and b and the distance between b and a. I know I could calculate the distances only once. I just didn’t bother to do that optimization.
2
APB9785
Creator of ECSx
A quick one today:
pairs
|> Enum.map(fn {{x1, y1}, {x2, y2}} ->
# Distance between two points
dx = x2 - x1
dy = y2 - y1
# Count how many empty rows or columns are in between
expanded_count =
Enum.count(state.empty_cols, fn col_idx ->
col_idx in x1..x2
end) +
Enum.count(state.empty_rows, fn row_idx ->
row_idx in y1..y2
end)
# Manhattan distance with the empty rows/columns expanded
abs(dx) + abs(dy) + expanded_count * (expansion_size - 1)
end)
|> Enum.sum()
Full solution here on Github
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