finish

lib/ruby_intro.rb

@@ -1,35 +1,60 @@
 # When done, submit this entire file to the autograder.
 
+# When done, submit this entire file to the autograder.
+
 # Part 1
 
 def sum(arr)
-  # YOUR CODE HERE
+  arr.reduce(0) { |acc, x| acc + x }
+
 end
 
 def max_2_sum(arr)
-  # YOUR CODE HERE
+  return 0 if arr.empty?
+  return arr[0] if arr.length == 1
+
+  sorted = arr.sort.reverse
+  sorted[0] + sorted[1]
 end
 
 def sum_to_n?(arr, n)
-  # YOUR CODE HERE
+  return false if arr.length < 2
+
+  seen = {}
+  arr.each do |num|
+    return true if seen[n - num]
+    seen[num] = true
 end
 
 # Part 2
 
 def hello(name)
-  # YOUR CODE HERE
+  "Hello, #{name}"
 end
 
 def starts_with_consonant?(s)
-  # YOUR CODE HERE
+  return false if s.nil? || s.empty?
+  /^[b-df-hj-np-tv-z]/i.match?(s)
 end
 
 def binary_multiple_of_4?(s)
-  # YOUR CODE HERE
+  return false unless /^[01]+$/.match?(s)
+  s.to_i(2) % 4 == 0
 end
 
 # Part 3
 
 class BookInStock
-  # YOUR CODE HERE
+  attr_reader :isbn, :price
+  attr_writer :isbn, :price
+
+  def initialize(isbn, price)
+    raise ArgumentError if isbn.empty? || price <= 0
+    @isbn = isbn
+    @price = price
+  end
+
+  def price_as_string
+    format("$%.2f", @price)
+  end
 end