palindrome.rb

# frozen_string_literal: true

require "test/unit/assertions"
include Test::Unit::Assertions

# the easiest implementation would be using .reverse method

def palindrome?(string)
  return true if string.size == 1 || string.empty?

  reversed = ""
  string = string.gsub(" ", "").downcase
  string.chars.reverse_each do |c|
    reversed << c
  end

  reversed == string
end

assert_equal palindrome?("abba"), true
assert_equal palindrome?("abbas"), false
assert_equal palindrome?("tattarrattat"), true
assert_equal palindrome?("Was it a palindrome?"), false
assert_equal palindrome?("No lemon, no melon"), true