Create Intcode module

2019/day5/intcode.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+module Intcode
+  def self.read(filename)
+    Program.new File.read(filename).split(',').map(&:to_i)
+  end
+
+  class Program
+    attr_reader :mem
+    def initialize(mem)
+      @mem = mem
+    end
+
+    def run(noun, verb)
+      mem = @mem.clone
+      mem[1] = noun
+      mem[2] = verb
+      pc = 0
+      loop do
+        case mem[pc]
+        when 1
+          r1 = mem[pc + 1]
+          r2 = mem[pc + 2]
+          r3 = mem[pc + 3]
+          mem[r3] = mem[r1] + mem[r2]
+          pc += 4
+        when 2
+          r1 = mem[pc + 1]
+          r2 = mem[pc + 2]
+          r3 = mem[pc + 3]
+          mem[r3] = mem[r1] * mem[r2]
+          pc += 4
+        when 99
+          return mem[0]
+        else
+          raise StandardError, "unexpected opcode: #{opcode}"
+        end
+      end
+    end
+  end
+end