Ruby refresher done

Gemfile

@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
-ruby '2.2.1'
+ruby '2.3.0'
 
 group :development do
   gem 'rspec'

lib/questions.rb

@@ -1,184 +1,221 @@
 # keep only the elements that start with an a
 def select_elements_starting_with_a(array)
+  array.select { |word| word[0] == 'a' }
 end
 
 # keep only the elements that start with a vowel
 def select_elements_starting_with_vowel(array)
+  array.select { |word| word.match(/^[aeiouy]/) }
 end
 
 # remove instances of nil (but NOT false) from an array
 def remove_nils_from_array(array)
+  array.select { |ele| !ele.nil? }
 end
 
 # remove instances of nil AND false from an array
 def remove_nils_and_false_from_array(array)
+  array.select { |ele| !ele.nil? && ele != false }
 end
 
 # don't reverse the array, but reverse every word inside it. e.g.
 # ['dog', 'monkey'] becomes ['god', 'yeknom']
 def reverse_every_element_in_array(array)
+  array.map(&:reverse)
 end
 
 # given an array of student names, like ['Bob', 'Dave', 'Clive']
 # give every possible pairing - in this case:
 # [['Bob', 'Clive'], ['Bob', 'Dave'], ['Clive', 'Dave']]
-# make sure you don't have the same pairing twice, 
+# make sure you don't have the same pairing twice,
 def every_possible_pairing_of_students(array)
+  array.combination(2).to_a
 end
 
-# discard the first 3 elements of an array, 
+# discard the first 3 elements of an array,
 # e.g. [1, 2, 3, 4, 5, 6] becomes [4, 5, 6]
 def all_elements_except_first_3(array)
+  array[3..-1]
 end
 
 # add an element to the beginning of an array
 def add_element_to_beginning_of_array(array, element)
+  array.insert(0, element)
 end
 
 # sort an array of words by their last letter, e.g.
 # ['sky', 'puma', 'maker'] becomes ['puma', 'maker', 'sky']
 def array_sort_by_last_letter_of_word(array)
+  array.sort { |x, y| x[-1] <=> y[-1] }
 end
 
 # cut strings in half, and return the first half, e.g.
 # 'banana' becomes 'ban'. If the string is an odd number of letters
 # round up - so 'apple' becomes 'app'
 def get_first_half_of_string(string)
+  string[0..-(string.length / 2 + 1)]
 end
 
 # turn a positive integer into a negative integer. A negative integer
 # stays negative
 def make_numbers_negative(number)
+  -number.abs
 end
 
-# turn an array of numbers into two arrays of numbers, one an array of 
+# turn an array of numbers into two arrays of numbers, one an array of
 # even numbers, the other an array of odd numbers
 # even numbers come first
 # so [1, 2, 3, 4, 5, 6] becomes [[2, 4, 6], [1, 3, 5]]
 def separate_array_into_even_and_odd_numbers(array)
+  [array.select(&:even?), array.select(&:odd?)]
 end
 
 # count the numbers of elements in an element which are palindromes
 # a palindrome is a word that's the same backwards as forward
 # e.g. 'bob'. So in the array ['bob', 'radar', 'eat'], there
 # are 2 palindromes (bob and radar), so the method should return 2
 def number_of_elements_that_are_palindromes(array)
+  array.count { |ele| ele == ele.reverse }
 end
 
 # return the shortest word in an array
 def shortest_word_in_array(array)
+  array.sort { |x, y| x.size <=> y.size }[0]
 end
 
 # return the shortest word in an array
 def longest_word_in_array(array)
+  array.sort { |x, y| y.size <=> x.size }[0]
 end
 
 # add up all the numbers in an array, so [1, 3, 5, 6]
 # returns 15
 def total_of_array(array)
+  array.inject { |sum, ele| sum += ele }
 end
 
 # turn an array into itself repeated twice. So [1, 2, 3]
 # becomes [1, 2, 3, 1, 2, 3]
 def double_array(array)
+  array.concat(array)
 end
 
 # convert a symbol into a string
 def turn_symbol_into_string(symbol)
+  symbol.to_s
 end
 
 # get the average from an array, rounded to the nearest integer
 # so [10, 15, 25] should return 17
 def average_of_array(array)
+  (array.inject { |sum, ele| sum += ele }.to_f / array.size).round
 end
 
 # get all the elements in an array, up until the first element
 # which is greater than five. e.g.
 # [1, 3, 5, 4, 1, 2, 6, 2, 1, 3, 7]
 # becomes [1, 3, 5, 4, 1, 2]
 def get_elements_until_greater_than_five(array)
+  array.take_while { |ele| ele <= 5 }
 end
 
 # turn an array (with an even number of elements) into a hash, by
 # pairing up elements. e.g. ['a', 'b', 'c', 'd'] becomes
 # {'a' => 'b', 'c' => 'd'}
 def convert_array_to_a_hash(array)
+  Hash[*array]
 end
 
 # get all the letters used in an array of words and return
 # it as a array of letters, in alphabetical order
 # . e.g. the array ['cat', 'dog', 'fish'] becomes
 # ['a', 'c', 'd', 'f', 'g', 'h', 'i', 'o', 's', 't']
 def get_all_letters_in_array_of_words(array)
+  array.join.split('').uniq.sort
 end
 
 # swap the keys and values in a hash. e.g.
 # {'a' => 'b', 'c' => 'd'} becomes
 # {'b' => 'a', 'd' => 'c'}
 def swap_keys_and_values_in_a_hash(hash)
+  hash.invert
 end
 
 # in a hash where the keys and values are all numbers
 # add all the keys and all the values together, e.g.
 # {1 => 1, 2 => 2} becomes 6
 def add_together_keys_and_values(hash)
+  hash.flatten.inject { |sum, ele| sum += ele }
 end
 
 # take out all the capital letters from a string
 # so 'Hello JohnDoe' becomes 'ello ohnoe'
 def remove_capital_letters_from_string(string)
+  string.tr('A-Z', '')
 end
 
 # round up a float up and convert it to an Integer,
 # so 3.214 becomes 4
 def round_up_number(float)
+  float.ceil
 end
 
 # round down a float up and convert it to an Integer,
 # so 9.52 becomes 9
 def round_down_number(float)
+  float.floor
 end
 
 # take a date and format it like dd/mm/yyyy, so Halloween 2013
 # becomes 31/10/2013
 def format_date_nicely(date)
+  "#{date.day}/#{date.month}/#{date.year}"
 end
 
 # get the domain name *without* the .com part, from an email address
 # so [email protected] becomes makersacademy
 def get_domain_name_from_email_address(email)
+  email[/@(.+)\.com/, 1]
 end
 
-# capitalize the first letter in each word of a string, 
+# capitalize the first letter in each word of a string,
 #  except 'a', 'and' and 'the'
 # *unless* they come at the start of the start of the string, e.g.
 # 'the lion the witch and the wardrobe' becomes
 # 'The Lion the Witch and the Wardrobe'
 def titleize_a_string(string)
+  string.capitalize.split(' ').each do |ele|
+    ele.capitalize! unless %w(a and the).index(ele)
+  end.join(' ')
 end
 
 # return true if a string contains any special characters
 # where 'special character' means anything apart from the letters
 # a-z (uppercase and lower) or numbers
 def check_a_string_for_special_characters(string)
+  string =~ /[^a-zA-Z1-9]+/ ? true : false
 end
 
 # get the upper limit of a range. e.g. for the range 1..20, you
 # should return 20
 def get_upper_limit_of(range)
+  range.max
 end
 
-# should return true for a 3 dot range like 1...20, false for a 
+# should return true for a 3 dot range like 1...20, false for a
 # normal 2 dot range
 def is_a_3_dot_range?(range)
+  range.include?(range.end) ? false : true
 end
 
 # get the square root of a number
 def square_root_of(number)
+  Math.sqrt(number)
 end
 
 # count the number of words in a file
 def word_count_a_file(file_path)
+  File.read(file_path).split(' ').count
 end
 
 # --- tougher ones ---
@@ -187,19 +224,37 @@ def word_count_a_file(file_path)
 # called call_method_from_string('foobar')
 # the method foobar should be invoked
 def call_method_from_string(str_method)
+  "test".send(:str_method)
 end
 
 # return true if the date is a uk bank holiday for 2014
 # the list of bank holidays is here:
 # https://www.gov.uk/bank-holidays
 def is_a_2014_bank_holiday?(date)
+  bank_holidays_2014 = [
+                            Time.new(2014, 1, 1),
+                            Time.new(2014, 4, 18),
+                            Time.new(2014, 1, 21),
+                            Time.new(2014, 5, 5),
+                            Time.new(2014, 8, 25),
+                            Time.new(2014, 12, 25),
+                            Time.new(2014, 12, 26)
+                       ]
+  bank_holidays_2014.include?(date)
 end
 
 # given your birthday this year, this method tells you
 # the next year when your birthday will fall on a friday
 # e.g. january 1st, will next be a friday in 2016
 # return the day as a capitalized string like 'Friday'
 def your_birthday_is_on_a_friday_in_the_year(birthday)
+  t = birthday
+  y = t.year
+  until t.friday?
+    y += 1
+    t = Time.new(y, t.month, t.day)
+  end
+  t.year
 end
 
 # in a file, total the number of times words of different lengths
@@ -208,19 +263,50 @@ def your_birthday_is_on_a_friday_in_the_year(birthday)
 # and 1 that is 4 letters long. Return it as a hash in the format
 # word_length => count, e.g. {2 => 1, 3 => 5, 4 => 1}
 def count_words_of_each_length_in_a_file(file_path)
+  hash_count = Hash.new
+  File.read(file_path).gsub!(/[^0-9A-Za-z]/, ' ').split(' ').each do |word|
+    hash_count[word.length] ||= 0
+    hash_count[word.length] += 1
+  end
+  hash_count
 end
 
 # implement fizzbuzz without modulo, i.e. the % method
 # go from 1 to 100
 # (there's no RSpec test for this one)
 def fizzbuzz_without_modulo
+  (0..99).each do |i|
+    x = ''
+    x += 'Fizz' if i / 3.to_f == (i / 3)
+    x += 'Buzz' if i / 5.to_f == (i / 5)
+    puts(x.empty? ? i : x)
+  end
 end
 
 # print the lyrics of the song 99 bottles of beer on the wall
 # http://www.99-bottles-of-beer.net/lyrics.html
-# make sure you use the singular when you have one bottle of 
+# make sure you use the singular when you have one bottle of
 # beer on the wall, and print 'no more bottles of beer on the wall'
 # at the end.
 # (there's no RSpec test for this one)
 def ninety_nine_bottles_of_beer
+  (0..99).to_a.reverse.each do |i|
+    if i == 0
+      string = "No more bottles of beer on the wall, "\
+       "no more bottles of beer.\n"\
+      "Go to the store and buy some more, "\
+      "99 bottles of beer on the wall.\n\n"
+    elsif i == 1
+      string = "1 bottle of beer on the wall, "\
+       "1 bottle of beer.\n"\
+      "Take one down and pass it around, "\
+      "no more bottles of beer on the wall.\n\n"
+    else
+      string = "#{i} bottles of beer on the wall, "\
+       "#{i} bottles of beer.\n"\
+      "Take one down and pass it around, "\
+      "#{i - 1} bottles of beer on the wall.\n\n"
+    end
+    puts string
+  end
 end