first teenagersprogramming weekly challenge submission

# Challenge week 1
# 3/23/15
# Meshiest / _cake

# Test data:
# psghactuxjnmrbyzefklwvoidq
# uammy oyfmh!

puts "Enter cipher: "
cipher = gets.chomp

unless /((?!=\G)([a-z])){26}/i =~ cipher
    puts "Invalid cipher, requires 26 unique letters"
    exit
end

map = Hash[*((cipher.chars.zip ('a'..'z').to_a).flatten)] # Map alphabet to each cipher character

puts "Enter ciphertext: "
text = gets.chomp

text = text.downcase
    .chars
    .map{ |c|
        map[c] || c # get the alternate character, otherwise, the same character
    } * ''

puts "Deciphered text: "
puts text