From ebbe992dead3deb36244d1d2f36c506ae298f76c Mon Sep 17 00:00:00 2001
From: Ariejan de Vroom <ariejan@devroom.io>
Date: Sat, 7 Dec 2024 06:43:45 +0100
Subject: [PATCH] Day 7 - Puzzle 2

Ruby FTW
---
 lib/solutions/day_07.rb       | 19 +++++++++++++------
 spec/solutions/day_07_spec.rb |  2 +-
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/lib/solutions/day_07.rb b/lib/solutions/day_07.rb
index acc714e..d1ad1fb 100644
--- a/lib/solutions/day_07.rb
+++ b/lib/solutions/day_07.rb
@@ -2,20 +2,26 @@ class Day07
   attr_accessor :equations
 
   def part_one(input)
-    @equations = input.split("\n").map { |l| Equation.new(l) }
+    @equations = input.split("\n").map { |l| Equation.new(l, %i[+ *]) }
     @equations.select { |e| e.valid? }.map(&:result).sum
   end
 
   def part_two(input)
-    0
+    @equations = input.split("\n").map { |l| Equation.new(l, %i[+ * pipes]) }
+    @equations.select { |e| e.valid? }.map(&:result).sum
+  end
+end
+
+class Numeric
+  # Monkey patching to add a pipe method to numbers
+  def pipes(other)
+    (to_s + other.to_s).to_i
   end
 end
 
 class Equation
   attr_accessor :result, :inputs
 
-  OPERATORS = %i[+ *]
-
   def valid?
     try_combinations(@inputs[0], 1)
   end
@@ -23,14 +29,15 @@ def valid?
   def try_combinations(total, idx)
     return total == @result if idx == @inputs.size
 
-    OPERATORS.each do |op|
+    @operators.each do |op|
       new_value = total.send(op, @inputs[idx])
       return true if try_combinations(new_value, idx + 1)
     end
     false
   end
 
-  def initialize(input)
+  def initialize(input, operators)
+    @operators = operators
     parts = input.split(':')
     @result = parts[0].to_i
     @inputs = parts[1].split(' ').map(&:to_i)
diff --git a/spec/solutions/day_07_spec.rb b/spec/solutions/day_07_spec.rb
index 53bb73b..f9707a5 100644
--- a/spec/solutions/day_07_spec.rb
+++ b/spec/solutions/day_07_spec.rb
@@ -12,7 +12,7 @@
 
   describe '#part_two' do
     it 'calculates the correct solutions for part two' do
-      expect(subject.part_two(input)).to eq(0)
+      expect(subject.part_two(input)).to eq(11_387)
     end
   end
 end