Solved Part 2

day03/input.sample.txt

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010

day03/solution.rb

@@ -0,0 +1,43 @@
+#!/bin/env ruby
+
+# Part 1
+report = File.readlines('./input').map(&:strip)
+masks = []
+report[0].length.times { masks.push(2**_1) }
+report.map! { _1.to_i(2) }
+gamma = 0
+
+masks.each do |mask|
+  gamma += mask if report.map { mask & _1 }.reject(&:zero?).count > report.count / 2
+end
+
+epsilon = gamma ^ masks.sum
+puts "Gamma is #{gamma}"
+puts "Epsilon is #{epsilon}"
+puts "Power is #{gamma * epsilon}"
+
+# Part 2
+def get_rating(report, masks, invert)
+  report_copy = report.clone
+  masks.each do |mask|
+    common = invert ? 1 : 0
+    if report_copy.map { mask & _1 }.reject(&:zero?).count >= report_copy.count / 2.to_f
+      common = invert ? 0 : 1
+    end
+    report_copy.reject! do |number|
+      if common.zero?
+        (mask & number).zero? ? false : true
+      else
+        (mask & number).zero? ? true : false
+      end
+    end
+    return report_copy[0] if report_copy.count == 1
+  end
+end
+
+masks.reverse!
+o2 = get_rating(report, masks, false)
+co2 = get_rating(report, masks, true)
+puts "Oxygen rating is #{o2}"
+puts "CO2 rating is #{co2}"
+puts "Life Support rating is #{o2 * co2}"