Transposition Decrypter

Transposition Decrypter

  def transposition_decrypter(key) 
# Calculate the length of columns based on the message length and how many letters in this key attempt
    col_length = (@encrypted_message.length) / key

    answer = []
      
    group_count = 0
    groups = {}

# Create character groups for each column + 1 so we start at 1 for readability
    (key + 1).times do |n|
      groups.merge!({n => [] })
    end

# Split all characters into groups of the pre determined col_length using modulo, associated with their group number. 
# The first group of 168 chars have group number 1. When the chars index gets to 168, start adding the chars to the next group.
# Going along until all chars are grouped by their columns. In this case evenly with no remainder.
     @encrypted_message.chars.each_with_index do |char, index|
      if index.modulo(col_length) == 0
        group_count = group_count + 1
      end
      groups[group_count] << char
     end
     
# As each group has an even amount of chars, we can iterate over that many times (168). Each iteration pulls out the same char from each group, adding it to the answer which at the end is the answer.  
     col_length.times do |i|
      (key + 1).times do |j|
        answer << groups[j][i]
      end
     end

    answer
  end