Implement Utils Class

app/services/utils.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class Utils
+  def self.previous_power_of_two(number)
+    return 0 if number.zero?
+
+    exponent = Math.log2 number
+    2**exponent.floor
+  end
+
+  def self.next_power_of_two(number)
+    return 1 if number.zero?
+
+    2 * previous_power_of_two(number)
+  end
+
+  def self.po2?(number)
+    number.to_s(2).count('1') == 1
+  end
+end

spec/services/utils_spec.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+RSpec.describe Utils do
+  [
+    { test: 5, result: 4 },
+    { test: 3, result: 2 },
+    { test: 13, result: 8 },
+    { test: 35, result: 32 },
+    { test: 32, result: 32 },
+    { test: 0, result: 0 },
+    { test: 3482, result: 2048 },
+    { test: 1337, result: 1024 }
+  ].each do |parameters|
+    it "calculates #{parameters[:result]} as previous power of two from #{parameters[:test]}" do
+      expect(Utils.previous_power_of_two(parameters[:test])).to eq(parameters[:result])
+    end
+  end
+
+  [
+    { test: 5, result: 8 },
+    { test: 3, result: 4 },
+    { test: 13, result: 16 },
+    { test: 35, result: 64 },
+    { test: 32, result: 64 },
+    { test: 0, result: 1 },
+    { test: 3482, result: 4096 },
+    { test: 1337, result: 2048 }
+  ].each do |parameters|
+    it "calculates #{parameters[:result]} as previous power of two from #{parameters[:test]}" do
+      expect(Utils.next_power_of_two(parameters[:test])).to eq(parameters[:result])
+    end
+  end
+
+  [
+    { test: 5, result: false },
+    { test: 3, result: false },
+    { test: 16, result: true },
+    { test: 4, result: true },
+    { test: 32, result: true },
+    { test: 0, result: false },
+    { test: 3482, result: false },
+    { test: 8192, result: true }
+  ].each do |parameters|
+    is_isnt = "isn't" unless parameters[:result]
+    is_isnt = 'is' if parameters[:result]
+    it "thinks #{parameters[:test]} #{is_isnt} a power of two" do
+      expect(Utils.po2?(parameters[:test])).to eq(parameters[:result])
+    end
+  end
+end