puzzles.rb

# В системе авторизации есть ограничение:
# логин должен начинаться с латинской буквы,
# состоять из латинских букв, цифр, точки и минуса,
# но заканчиваться только латинской буквой или цифрой;
# минимальная длина логина — один символ, максимальная — 20.
# Напишите код, проверяющий соответствие входной строки этому правилу. Придумайте несколько способов решения задачи и сравните их.

class AuthOne
  def initialize login
    @login = login
    @regexp = /^[a-zA-z]{1}[a-zA-Z0-9\.\-]{0,18}[a-zA-z0-9]$/
  end

  def authorization
    @regexp.match(@login).nil? ? 'Access denied' : 'You successfully authorized'
  end
end

class AuthTwo
  def initialize login
    @login = login.downcase
    @letters = ('a'..'z').to_a
    @numbers = ('0'..'9').to_a
    @symbols = %w(. -)
  end

  def authorization
    length_pass? && first_letter_pass? && middle_letters_pass? && last_letter_pass? ? 'You successfully authorized' : 'Access denied'
  end

  private
  def length_pass?
    (1..20).include? @login.length
  end

  def first_letter_pass?
    @letters.include? @login.chars.first
  end

  def middle_letters_pass?
    @login[1..18].chars.all? { |char| (@letters + @numbers + @symbols).include?(char) }
  end

  def last_letter_pass?
    (@letters + @numbers).include? @login.chars.last
  end
end



# Есть два списка разной длины. В первом содержатся ключи, а во втором значения.
# Напишите функцию, которая создаёт из этих ключей и значений словарь.
# Если ключу не хватило значения, в словаре должно быть значение None.
# Значения, которым не хватило ключей, нужно игнорировать.

class Dictionary

  def initialize
    @keys = %w(key1 key2 key3 key4 key5)
    @values = %w(1 2 3 4)
    @index = 0
  end

  def output
    @keys.inject({}) do |memo, key|
      @values[@index].nil? ? memo[key] = "None" : memo[key] = @values[@index]
      @index += 1
      memo
    end
  end

end



# Description:
# The word i18n is a common abbreviation of internationalization the developer community use instead of typing the whole word and trying to spell it correctly. Similarly, a11y is an abbreviation of accessibility.
# Write a function that takes a string and turns any and all words within that string of length 4 or greater into an abbreviation following the same rules.

# Notes:
# A "word" is a sequence of alphabetical characters. By this definition, if there is a hyphen (eg. "elephant-ride"), this will produce two, one on either side (eg. "elephant" and "ride").
# The abbreviated version of the word should have the first letter, then the number of removed characters, then the last letter (eg. "e6t-r2e").

class Abbreviator
  def self.abbreviate(string)
    string.gsub(/(\w{4,})/) { |word| "#{word.chars.first}#{word.length-2}#{word.chars.last}" }
  end
end



# Description:
# A palindrome is a word, phrase, number, or other sequence of symbols or elements, whose meaning may be interpreted the same way in either forward or reverse direction. Famous examples include "Amore, Roma", "A man, a plan, a canal: Panama" and "No 'x' in 'Nixon'". - wikipedia
# Our goal is to determine whether or not a given string is a valid palindrome or not.
# Like the above examples, here are a few test cases which are also populated:
# "Amore, Roma" => valid
# "A man, a plan, a canal: Panama" => valid
# "No 'x' in 'Nixon'" => valid
# "Abba Zabba, you're my only friend" => invalid

def palindrome(string)
  str = string.gsub(/[^0-9a-zA-Z]+/, '').downcase
  str == str.split(//).reduce([]) {|acc, x| [x] + acc}.join
end



# Description:
# Write a function that accepts an array of 10 integers (between 0 and 9), that returns a string of those numbers in the form of a phone number.
# Example:
# createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]) => returns "(123) 456-7890"
# The returned format must be correct in order to complete this challenge. 
# Don't forget the space after the closing parenthese!

def createPhoneNumber(numbers)
  numbers.join.gsub(/([0-9]{3})([0-9]{3})([0-9]{4})/, '(\1) \2-\3')
end



# Description:
# Write a function that accepts a string, and returns true if it is in the form of a phone number. 
# Assume that any integer from 0-9 in any of the spots will produce a valid phone number.

# Only worry about the following format:
# (123) 456-7890 (don't forget the space after the close parentheses) 

# Examples:
# validPhoneNumber("(123) 456-7890")  =>  returns true
# validPhoneNumber("(1111)555 2345")  => returns false
# validPhoneNumber("(098) 123 4567")  => returns false

def validPhoneNumber(phoneNumber)
  phoneNumber.scan(/^\([0-9]{3}+\)\s[0-9]+\-[0-9]{4}$/).length > 0 ? true : false
end



# Description:
# Complete the squareSum method so that it squares each number passed into it and then sums the results together.
# For example:
# squareSum([1, 2, 2]) # should return 9

def squareSum(numbers)
  numbers.map.inject{|sum, element| sum + element**2}
end



# Description:
# Your goal is to write the group_and_count method, which should receive and array as unique parameter and return a hash. Empty or nil input must return nil instead of a hash. This hash returned must contain as keys the unique values of the array, and as values the counting of each value.
# Example usage:
# input = [1,1,2,2,2,3]
# group_and_count(input)# == {1=>2, 2=>3, 3=>1}

# The following methods were disabled:
# Array#count
# Array#length

def group_and_count(input)
  input.nil? || input.empty? ? nil : input.inject(Hash.new(0)){ |hash, v| hash[v] = hash[v]+1; hash }
end