Ruby crash course

anagrams.rb

def anagrams?(a, b)
  frequencies_a = get_frequencies(a)
  frequencies_b = get_frequencies(b)

  if frequencies_a.length != frequencies_b.length
    return false
  end

  frequencies_a.each do |key, value|
    if value != frequencies_b[key]
      return false
    end
  end

  true
end

def get_frequencies(string)
  frequency_map = {}

  string.split("").each do |c|
    unless frequency_map.key?(c)
      frequency_map[c] = 0
    end

    frequency_map[c] += 1
  end

  frequency_map
end

puts anagrams?("binary", "brainy")
puts anagrams?("iamlordvoldemort", "tommarvoloriddle")
puts anagrams?("aaabbc", "aaabbd")

balanced_braces.rb

def balanced?(string)
  opening_braces = ["{", "[", "("]
  closing_braces = ["}", "]", ")"]

  stack = []

  string.split("").each do |c|
    opening_pos = opening_braces.index(c)

    if opening_pos != nil
      stack.push(c)
      puts "Char #{c} pushed to stack"
      next
    else
      if stack.length == 0
        puts "Char #{c} found but stack is empty"
        return false
      end

      stack_top = stack.pop
      puts "Char #{c} popped char #{stack_top} from stack"

      closing_pos = closing_braces.index(c)
      opening_pos = opening_braces.index(stack_top)

      if closing_pos != opening_pos
        puts "Char #{c} doesn't match char #{stack_top} on top of the stack"
        return false
      end
    end
  end

  return stack.length == 0
end

puts balanced?("{}()[]")
puts balanced?("{[()]}")
puts balanced?("{{[[(())]]}}")

puts balanced?("()]")
puts balanced?("{[)}")
puts balanced?("{[(])}")

mask_email_address.rb

def mask_email_address(email_address = "")
  parts = email_address.split("@")

  if parts.length == 0
    return "***@**"
  end
  
  masked_email_address = parts[0][0..1] + "***"
  
  if parts[1] != nil
    masked_email_address += "@"

    masked_domain_parts = parts[1].split(".").map do |domain_part|
      domain_part[0] + "**"
    end

    masked_email_address += masked_domain_parts.join(".")
  end

  masked_email_address
end

puts mask_email_address
puts mask_email_address("")
puts mask_email_address("eduardo")
puts mask_email_address("eduardo@localhost")
puts mask_email_address("eduardo@garcia.mx")
puts mask_email_address("eduardo@garcia.espinosa.mx")

palindrome.rb

def palindrome?(string)
  steps = (string.length / 2.0).floor

  for i in 0...steps do
    reverse_i = string.length - i - 1

    puts "Comparing #{string[i]} at index #{i} vs #{string[reverse_i]} at index #{reverse_i}"

    if string[i] != string[reverse_i]
      return false
    end
  end

  true
end

puts palindrome?("racecar")
puts palindrome?("anitalavalatina")
puts palindrome?("vetustamorla")