pushing up ruby-monk exercises

SamGerber · SamGerber · commit 3db80209c649 · 2015-10-31T19:20:16.000-05:00
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/05-string_length_finder.rb b/pre-course/01-ruby_monk/00-ruby_primer/05-string_length_finder.rb
@@ -0,0 +1,20 @@
+# Problem Statement
+# Given an array containing some strings, return an array containing the
+# length of those strings.
+#
+# You are supposed to write a method named 'length_finder' to accomplish
+# this task.
+#
+# Example:
+# Given ['Ruby','Rails','C42'] the method should return [4,5,3]
+
+#https://rubymonk.com/learning/books/1-ruby-primer/problems/5-string-length-finder
+
+
+def length_finder(words)
+  lengths = {}
+  words.each do |word|
+    lengths[word] = word.length
+  end
+  lengths.values
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/06-frequency_finder.rb b/pre-course/01-ruby_monk/00-ruby_primer/06-frequency_finder.rb
@@ -0,0 +1,21 @@
+# Problem Statement
+# Given a sentence containing multiple words, find the frequency of a given
+# word in that sentence.
+#
+# Construct a method named 'find_frequency' which accepts two arguments
+# 'sentence' and 'word', both of which are String objects.
+#
+# Example: The method, given 'Ruby is The best language in the World'
+# and 'the', should return 2 (comparison should be case-insensitive).
+#
+# Hint: You can use the method Array#count to count the frequency of
+# any element in the given array. eg:
+#
+# [9,3,4,9,5].count(9)
+# Will return the value 2
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/6-frequency-finder
+
+def find_frequency(sentence, word)
+  sentence.downcase.split.count(word.downcase)
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/09-calculator.rb b/pre-course/01-ruby_monk/00-ruby_primer/09-calculator.rb
@@ -0,0 +1,15 @@
+# Problem Statement
+# Create a class Calculator, which performs addition and subtraction of
+# two numbers at a time. The sample code explains the expected API.
+
+#https://rubymonk.com/learning/books/1-ruby-primer/problems/9-calculator
+
+class Calculator
+  def add(a, b)
+   a + b
+  end
+
+  def subtract(a, b)
+   a - b
+  end
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/14-sort_string_words.rb b/pre-course/01-ruby_monk/00-ruby_primer/14-sort_string_words.rb
@@ -0,0 +1,20 @@
+# Problem Statement
+# Create a method named 'sort_string' which accepts a String and
+# rearranges all the words in ascending order, by length.
+# Let's not treat the punctuation marks any different than other characters
+#  and assume that we will always have single space to separate the words.
+#
+# Example: Given a string "Sort words in a sentence", it should return
+# "a in Sort words sentence".
+#
+# Note: You can use the sort method to sort an array. Try the documentation
+#  at ruby-lang to know more about sort.
+#
+#  https://rubymonk.com/learning/books/1-ruby-primer/problems/14-sort-string-words
+
+def sort_string(string)
+  words = string.split.sort do |word1, word2|
+    word1.length <=> word2.length
+  end
+  words.join(" ")
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/143-palindrome.rb b/pre-course/01-ruby_monk/00-ruby_primer/143-palindrome.rb
@@ -0,0 +1,16 @@
+# Problem Statement
+# Given a sentence, return true if the sentence is a palindrome.
+#
+# You are supposed to write a method palindrome? to accomplish this task.
+#
+# Note Ignore whitespace and cases of characters.
+#
+# Example:
+# Given "Never odd or even" the method should return true
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/143-palindrome
+
+def palindrome?(sentence)
+  downcase_stripped_sentence = sentence.downcase.gsub(" ", "")
+  downcase_stripped_sentence  ==  downcase_stripped_sentence.reverse
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/144-sum_of_cubes.rb b/pre-course/01-ruby_monk/00-ruby_primer/144-sum_of_cubes.rb
@@ -0,0 +1,12 @@
+# Problem Statement
+# Compute the sum of cubes for a given range a through b.
+#
+# Write a method called sum_of_cubes to accomplish this task
+#
+# Example Given range 1 to 3 the method should return 36
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/144-sum_of_cubes
+
+def sum_of_cubes(a, b)
+  (a..b).inject(0) { |sum, x| sum += (x*x*x) }
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/147-non_duplicate_values.rb b/pre-course/01-ruby_monk/00-ruby_primer/147-non_duplicate_values.rb
@@ -0,0 +1,18 @@
+# Problem Statement
+# Given an Array, return the elements that are present exactly once in
+# the array.
+#
+# You need to write a method called non_duplicated_values to accomplish
+# this task.
+#
+# Example: Given [1,2,2,3,3,4,5], the method should return [1,4,5]
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/147-non-duplicate-values
+
+def non_duplicated_values(values)
+  results = []
+  values.each do |value|
+    results << value if values.count(value) == 1
+  end
+  results
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/148-array_of_fixnum.rb b/pre-course/01-ruby_monk/00-ruby_primer/148-array_of_fixnum.rb
@@ -0,0 +1,13 @@
+# Problem Statement
+# Given an array, return true if all the elements are Fixnums.
+#
+# You need to write array_of_fixnums? method to accomplish this task.
+#
+# Example:
+# Given [1,2,3], the method should return true
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/148-array_of_fixnum
+
+def array_of_fixnums?(array)
+  array.inject(0) {|result, element| result = result && element.is_a?(Fixnum)}
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/15-select_random_elements_from_an_array.rb b/pre-course/01-ruby_monk/00-ruby_primer/15-select_random_elements_from_an_array.rb
@@ -0,0 +1,27 @@
+# Problem Statement
+# Create a method 'random_select' which, when given an array of elements
+#  (array) and a number (n), returns n randomly selected elements from
+#   that array.
+#
+# Example: Given an array [1, 2, 3, 4, 5] and 2 should return two random
+#  numbers from the given array. (Note: those two random numbers may be
+#  the same number.) The method should return those random values in a
+#  new array.
+#
+# Calling the method twice should ideally return different sets of values
+# (though it may not).
+#
+# Note: Ruby has the method rand which takes a parameter max. It returns
+#  a random number lesser than max.
+#
+# One more note: Ruby also has a method Array#sample which very concisely
+#  solves this problem. Unfortunately, it's too concise! The exercise is
+#  almost to write your own Array#sample, so it's been disallowed. Good luck!
+#
+#  https://rubymonk.com/learning/books/1-ruby-primer/problems/15-select-random-elements-from-an-array
+#
+def random_select(array, n)
+  result = []
+  n.times {result << array[rand(n)]}
+  result
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/150-kaprekars_number.rb b/pre-course/01-ruby_monk/00-ruby_primer/150-kaprekars_number.rb
@@ -0,0 +1,22 @@
+# Problem Statement
+#
+# 9 is a Kaprekar number since
+# 9 ^ 2 = 81 and 8 + 1 = 9
+#
+# 297 is also Kaprekar number since
+# 297 ^ 2 = 88209 and 88 + 209 = 297.
+#
+# In short, for a Kaprekar number k with n-digits, if you square it and add
+# the right n digits to the left n or n-1 digits, the resultant sum is k.
+# Find if a given number is a Kaprekar number.
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/150-kaprekar-s-number
+
+def kaprekar?(k)
+  no_of_digits = k.to_s.size
+  square = (k ** 2).to_s
+
+  second_half = square[-no_of_digits..-1]
+  first_half = square.size.even? ? square[0..no_of_digits-1] : square[0..no_of_digits-2]
+
+  k == first_half.to_i + second_half.to_i
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/152-color_contrast.rb b/pre-course/01-ruby_monk/00-ruby_primer/152-color_contrast.rb
@@ -0,0 +1,46 @@
+# Problem Statement
+# For 2 Colors in RGB:
+# (R1, G1, B1) and (R2, G2, B2),
+#
+# Brightness index is:
+# ( 299*R1 + 587*G1 + 114*B1) / 1000
+#
+# Brightness difference is:
+# Absolute difference in brighness indices
+#
+# Hue difference is:
+# |R1 - R2| + |G1 - G2| + |B1 - B2|
+# where |x| is the absolute value of x
+#
+# If Brightness difference is more than 125 and the Hue difference is more
+#  than 500 then the colors have sufficient contrast
+#
+# Find out if the given color combos have sufficient contrast and get
+# all the tests passing.
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/152-color-contrast
+
+class Color
+  attr_reader :r, :g, :b
+  def initialize(r, g, b)
+    @r = r
+    @g = g
+    @b = b
+  end
+
+  def brightness_index
+    (299 * @r + 587 * @g + 114 * @b) / 1000
+  end
+
+  def brightness_difference(another_color)
+    (another_color.brightness_index - self.brightness_index).abs
+  end
+
+  def hue_difference(another_color)
+    (another_color.r - self.r).abs + (another_color.g - self.g).abs + (another_color.b - self.b).abs
+  end
+
+  def enough_contrast?(another_color)
+    self.brightness_difference(another_color) > 125 && self.hue_difference(another_color) >500
+  end
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/153-measure_time_to_run_code.rb b/pre-course/01-ruby_monk/00-ruby_primer/153-measure_time_to_run_code.rb
@@ -0,0 +1,15 @@
+# Problem Statement
+#
+# You are given some code in the form of lambdas.
+#
+# Measure and return the time taken to execute that code.
+#
+# You may use Time.now to get the current time.
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/153-measure-time-to-run-code
+
+def exec_time(proc)
+  begin_time = Time.now
+  proc.call
+  Time.now - begin_time
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/154-permutations.rb b/pre-course/01-ruby_monk/00-ruby_primer/154-permutations.rb
@@ -1,3 +1,13 @@
+# Problem Statement
+# Given a 3 or 4 digit number with distinct digits, return a sorted array
+# of all the unique numbers that can be formed with those digits.
+#
+# Example:
+# Given: 123
+# Return: [123, 132, 213, 231, 312, 321]
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/154-permutations
+
 def number_shuffle(number)
   results = []
   if number < 100
@@ -19,7 +29,5 @@ def number_shuffle(number)
       end
     end
   end
-  return results.uniq.sort
+  return results.sort
 end
-
-puts number_shuffle(123456789)
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/155-restaurant.rb b/pre-course/01-ruby_monk/00-ruby_primer/155-restaurant.rb
@@ -0,0 +1,30 @@
+# Problem Statement
+# A restaurant has incoming orders for which you need to compute the costs
+# based on the menu.
+#
+# You might get multiple orders at times.
+#
+# Examples:
+# if the order is {:rice => 1, :noodles => 1}, and the menu is
+#   {:rice => 3, :noodles => 2}, then the cost is 5.
+#
+# If the orders are {:rice => 1, :noodles => 1} and {:rice => 2, :noodles => 2}
+#  and the menu is {:rice => 3, :noodles => 2}, then the cost is 15.
+#
+#  https://rubymonk.com/learning/books/1-ruby-primer/problems/155-restaurant
+
+class Restaurant
+  def initialize(menu)
+    @menu = menu
+  end
+
+  def cost(*orders)
+    sum = 0
+    orders.each do |order|
+      order.each do |item, quantity|
+        sum += quantity * @menu[item]
+      end
+    end
+  sum
+  end
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/156-sum.rb b/pre-course/01-ruby_monk/00-ruby_primer/156-sum.rb
@@ -0,0 +1,25 @@
+# Problem Statement
+# Given a custom class MyArray,
+# write a 'sum' method that takes a block parameter.
+#
+# Example:
+# my_array = MyArray.new([1, 2, 3])
+# my_array.sum gives 6
+# my_array.sum(10) gives 16
+# my_array.sum(0) {|n| n ** 2 } gives 14
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/156-sum
+
+class MyArray
+  attr_reader :array
+
+  def initialize(array)
+    @array = array
+  end
+
+  def sum(initial_value = 0)
+    return array.inject(:+) + initial_value unless block_given?
+    sum = initial_value
+    array.each {|x| sum += yield(x) }
+    sum
+  end
+end
diff --git a/pre-course/01-ruby_monk/00-ruby_primer/50-hiring_programmers_ruby_boolean_expressions.rb b/pre-course/01-ruby_monk/00-ruby_primer/50-hiring_programmers_ruby_boolean_expressions.rb
@@ -0,0 +1,36 @@
+# Problem Statement
+# Let us say you are trying to recruit team-members for your new startup!
+# Given a candidate, you need an expression that will tell you whether they
+# fit into certain types. This is how a candidate object would look:
+#
+# candidate.years_of_experience = 4
+#   candidate.github_points = 293
+#   candidate.languages_worked_with = ['C', 'Ruby', 'Python', 'Clojure']
+#   candidate.applied_recently? = false
+#   candidate.age = 26
+# We are looking to hire experienced Ruby programmers. Our ideal candidate
+# has 2 or more years of experience, but some programmers become really good
+# even before that. We'll consider their Github points (a nice indicator of
+# a good programmer), and even if they are not experienced, candidates with
+# 500 Github points or more can apply. And there is one more catch: Ruby being
+# a cool and awesome language, a lot of smart youngsters are very good at it.
+# We love those kids, but for this particular job we'd rather have them study
+# at school than work. Let us filter out candidates who are younger than 15.
+# Also we don't want to consider candidates who applied recently for this
+# opening.
+#
+# If you haven't solved these types of expressions before, try getting one
+# condition right at a time. For each condition you get correct, some tests
+# will start passing. As your expression matures to take care of all the
+# criteria, all the tests will pass and you'll have a green flag. Now, march on!
+#
+# https://rubymonk.com/learning/books/1-ruby-primer/problems/50-hiring_programmers_ruby_boolean_expressions
+
+is_an_experienced_programmer = (
+  (
+    candidate.years_of_experience >= 2 ||
+    candidate.github_points >= 500)
+  ) &&
+  candidate.languages_worked_with.include?("Ruby") &&
+  !(candidate.age < 15) &&
+  !candidate.applied_recently?
diff --git a/pre-course/01-ruby_monk/01-orders-and-costs.rb b/pre-course/01-ruby_monk/01-orders-and-costs.rb
