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# HELPER METHODS
def trim(word)
  word[1..-2]
end

def first_and_last_chars_match?(word)
  word[0] == word[-1]
end

def less_than_two_chars?(word)
  word.length < 2
end



# ITERATIVE SOLUTION

# UNTIL word has less than two characters
#   IF first and last letters do not match
#     NO, not a palindrome
#   ELSE
#     REMOVE first and last letters
#     LOOP
# YES a palindrome

def iterative_is_palindrome?(word)
  until less_than_two_chars?(word)
    return false unless first_and_last_chars_match?(word)
    word = trim(word)
  end
  return true
end



# RECURSIVE SOLUTION

# BASE CASE:  Palindrome if word has less than two characters
# IF first and last letters do not match
#   NO, not a palindrome
# REMOVE first and last letters and check again

def recursive_is_palindrome?(word)
  return true if less_than_two_chars?(word)
  return false unless first_and_last_chars_match?(word)
  recursive_is_palindrome?(trim(word))
end



# Driver Code
puts iterative_is_palindrome?("civic") == true
puts iterative_is_palindrome?("dog")   == false
puts recursive_is_palindrome?("civic") == true
puts recursive_is_palindrome?("dog")   == false