Part 2

ruby/2025/6/bin/problem

@@ -2,4 +2,5 @@
 require "cephalopod_math"
 
 cephalopod_math = CephalopodMath.for STDIN.read.chomp
-puts "Part 1: #{cephalopod_math.wide_column_answers.sum}"
+puts "Part 1: #{cephalopod_math.wide_problem_answers.sum}"
+puts "Part 2: #{cephalopod_math.narrow_problem_answers.sum}"

ruby/2025/6/lib/cephalopod_math.rb

@@ -8,11 +8,38 @@ class CephalopodMath
     new input
   end
 
-  def wide_columns
-    worksheet.split("\n").map(&:split).transpose
+  def wide_problem_answers
+    problems.map do |problem|
+      problem[..-2].map(&:to_i).reduce(&(problem[-1].strip.to_sym))
+    end
   end
 
-  def wide_column_answers
-    wide_columns.map{ |column| column[..-2].map(&:to_i).reduce(&(column[-1]).to_sym) }
+  def narrow_problem_answers
+    problems.map do |problem|
+      operator = problem[-1].strip.to_sym
+      numbers = problem[..-2].map { |line| line.split("") }.transpose.map { |line| line.join("").to_i }.reject(&:zero?)
+      numbers.reduce operator
+    end
+  end
+
+  def problem_widths
+    @problem_widths ||= operator_line.split("+").map { |c| c.split "*" }.flatten.map(&:length)[1..]
+  end
+
+  def problems
+    @problems ||= lines.map(&:clone).map do |line|
+      problem_widths.reduce([]) do |chunks, problem_width|
+        slice = line.slice!(0, problem_width + 1)
+        chunks << slice
+      end
+    end.transpose
+  end
+
+  def operator_line
+    lines.last
+  end
+
+  def lines
+    worksheet.split("\n")
   end
 end