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advent-of-code/2022/ruby/day_07.rb

70 lines
1.2 KiB

input = ARGF.read.lines(chomp: true).slice_when { _2.start_with?(?$) }
Dir = Struct.new(:parent, :name, :children) do
include Enumerable
def size = children.sum(&:size)
def each(&block)
return enum_for(__method__, &block) unless block
block.(self)
children.each do |child|
case child
when Dir
child.each(&block)
when File
block.(child)
else
fail child.inspect
end
end
end
end
File = Struct.new(:parent, :name, :size)
root = Dir.new(nil, ?/, [])
pwd = root
input.each do |chunk|
cmd, *out = *chunk
case cmd
when /\$ cd \//
# no-op
when /\$ cd \.\./
pwd = pwd.parent
when /\$ cd (.+)/
pwd = pwd.children.find { _1.name == $1 }
when /\$ ls/
out.each do |line|
case line
when /(\d+) (.+)/
pwd.children << File.new(pwd, $2, $1.to_i)
when /dir (.+)/
pwd.children << Dir.new(pwd, $1, [])
else
fail line
end
end
else
fail chunk.inspect
end
end
# part 1
p root.each
.select { Dir === _1 }
.map(&:size)
.select { _1 < 100_000 }
.sum
# part 2
p root.each
.select { Dir === _1 }
.map(&:size)
.sort
.find { _1 >= 30_000_000 - (70_000_000 - root.size) }