Advent of Code 2016, Day 6: Signals and Noise

Part A

On Day 6 we are working with columns of text. We have a bunch of strings in the input file and we need to calculate the most common character in each column. Each character is considered as a separate column.

Here is the solution:

data = File.readlines("6.txt", chomp: true)
columns = []
data[0].size.times { columns.push({ "max" => 0, "char" => nil }) }

data.each do |row|
  row.chars.each_with_index do |char, column|
    columns[column][char] ||= 0
    columns[column][char] += 1

    if columns[column][char] > columns[column]["max"]
      columns[column]["max"] = columns[column][char]
      columns[column]["char"] = char
    end
  end
end

message = columns.map { |column| column["char"] }.join
puts message

Part B

Second part is the least common character in each column:

data = File.readlines("6.txt", chomp: true)
columns = []
data[0].size.times { columns.push({}) }

data.each do |row|
  row.chars.each_with_index do |char, column|
    columns[column][char] ||= 0
    columns[column][char] += 1
  end
end

message = columns.map do |column|
  min = Float::INFINITY
  final_char = nil
  column.each do |char, value|
    if value < min
      min = value
      final_char = char
    end
  end
  final_char
end

puts message.join