2023: Day 11, part 2

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Wesley Moore 2023-12-11 19:19:40 +10:00
parent 083b47c23b
commit bb2ee520ab
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@ -1,9 +1,10 @@
MULTIPLIER = ENV["MULTIPLIER"].to_i || 2
input = ARGF.read.strip input = ARGF.read.strip
by_row = input.lines.map(&:rstrip).map { |line| line.split("") } by_row = input.lines.map(&:rstrip).map { |line| line.split("") }
def needs_expand(data) def needs_expand(data)
expand = [] expand = []
data.each_with_index { |row, i| expand << i if row.all? { |c| c == "." } } data.each_with_index { |row, i| expand << i if row.all? { |c| c == "." || c == "," } }
expand expand
end end
@ -16,16 +17,17 @@ end
# do expansion # do expansion
row_expand = needs_expand(by_row) row_expand = needs_expand(by_row)
row_expand.reverse.each do |i| row_expand.reverse.each do |i|
by_row.insert(i, by_row[i].dup) by_row[i] = ("," * by_row[i].length).split("") # add expansion marker
end end
by_column = by_row.transpose by_column = by_row.transpose
col_expand = needs_expand(by_column) col_expand = needs_expand(by_column)
col_expand.reverse.each do |i| col_expand.reverse.each do |i|
by_column.insert(i, by_column[i].dup) by_column[i] = ("," * by_column[i].length).split("") # add expansion marker
end end
cosmos = by_column.transpose cosmos = by_column.transpose
print_cosmos(cosmos)
# find galaxies # find galaxies
galaxies = [] galaxies = []
@ -39,4 +41,32 @@ def galaxy_distance(a, b)
(a[0] - b[0]).abs + (a[1] - b[1]).abs (a[0] - b[0]).abs + (a[1] - b[1]).abs
end end
puts "Part 1: #{galaxies.combination(2).map { |a, b| galaxy_distance(a, b) }.sum}" def cosmos_at(x, y, cosmos)
cosmos[y][x]
end
distances = galaxies.combination(2).map do |combo|
a, b = combo.sort
distance = galaxy_distance(a, b)
# see how many millions are crossed in x
x_millions = (a[0]..b[0]).filter_map do |x|
loc = cosmos_at(x, a[1], cosmos)
loc if loc == ","
end
# now y component
range = if a[1] > b[1]
b[1]..a[1]
else
a[1]..b[1]
end
y_millions = range.filter_map do |y|
loc = cosmos_at(b[0], y, cosmos)
loc if loc == ","
end
distance + ((x_millions.length + y_millions.length) * MULTIPLIER) - x_millions.length - y_millions.length
end
puts "Sum of distances with multiplier #{MULTIPLIER}: #{distances.sum}"