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def mask_address address, mask
address.chars.zip(mask.chars).map do |bit, mask_bit|
case mask_bit
when '0'
bit
when '1'
'1'
when 'X'
'X'
end
end.join ''
end
lines = File.readlines('input.txt')
mask = ''
code = []
lines.each do |line|
if line.slice(0, 4) == 'mask'
mask = line.split(' = ')[1].strip
else
split = line.split(/\[|\] = /)
address = split[1].to_i.to_s(2).rjust 36, '0'
value = split[2].to_i
code.push [mask_address(address, mask), value]
end
end
def enumerate_addresses address
first_x = address.index 'X'
if !first_x
return [address]
end
first_segment = address.slice(0, first_x)
rest = address.slice(first_x + 1, address.length)
enumerate_addresses(rest).flat_map do |a|
[
(first_segment + '0' + a),
(first_segment + '1' + a)
]
end
end
mem = Hash.new 0
code.each do |address, value|
addresses = enumerate_addresses address
addresses.each do |a|
mem[a] = value
end
end
sum = 0
mem.each_value do |v|
sum += v
end
puts sum
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