Day 24 Ruby solutions

Author: creideiki

24-1.rb

@@ -0,0 +1,125 @@
+#!/usr/bin/env ruby
+
+require 'memoist'  # https://github.com/matthewrudy/memoist
+
+class ALU
+  attr_accessor :w, :x, :y, :z
+
+  def initialize(input)
+    @input = input.split('').map(&:to_i)
+    @w = 0
+    @x = 0
+    @y = 0
+    @z = 0
+  end
+
+  def to_s
+    "<#{self.class}: input=#{@input}, w=#{@w}, x=#{@x}, y=#{@y}, z=#{@z}>"
+  end
+
+  def inspect
+    to_s
+  end
+
+  def inp(reg, _)
+    instance_variable_set('@' + reg, @input.shift.to_i)
+  end
+
+  def get_operand(oper)
+    case oper
+    when 'w'..'z'
+      instance_variable_get('@' + oper)
+    else
+      oper.to_i
+    end
+  end
+
+  def add(reg, oper)
+    op1 = instance_variable_get('@' + reg)
+    op2 = get_operand oper
+    instance_variable_set('@' + reg, op1 + op2)
+  end
+
+  def mul(reg, oper)
+    op1 = instance_variable_get('@' + reg)
+    op2 = get_operand oper
+    instance_variable_set('@' + reg, op1 * op2)
+  end
+
+  def div(reg, oper)
+    op1 = instance_variable_get('@' + reg)
+    op2 = get_operand oper
+    instance_variable_set('@' + reg, (op1.to_f / op2).truncate)
+  end
+
+  def mod(reg, oper)
+    op1 = instance_variable_get('@' + reg)
+    op2 = get_operand oper
+    instance_variable_set('@' + reg, op1 % op2)
+  end
+
+  def eql(reg, oper)
+    op1 = instance_variable_get('@' + reg)
+    op2 = get_operand oper
+    instance_variable_set('@' + reg, op1 == op2 ? 1 : 0)
+  end
+
+  def valid?
+    @z == 0
+  end
+end
+
+class MONAD
+  extend Memoist
+
+  @@instruction_format = /^(?<inst>inp|add|mul|div|mod|eql) (?<reg>[w-z])($| (?<oper>([w-z]|[[:digit:]\-]+)))/
+
+  def initialize(program)
+    @blocks = []
+    collect = []
+    program.each do |line|
+      if line.start_with? 'inp' and not collect.empty?
+        @blocks.append collect
+        collect = []
+      end
+      collect.append line
+    end
+    @blocks.append collect
+  end
+
+  def run_block(step, w, z)
+    alu = ALU.new w.to_s
+    alu.z = z
+    @blocks[step].each do |insn|
+      @@instruction_format.match(insn) do |m|
+        alu.send m['inst'].to_sym, m['reg'], m['oper']
+      end
+    end
+    alu.z
+  end
+
+  def find_solution(step, input, last_output)
+    return '' if step == 14 and last_output.zero?
+    return nil if step == 14
+
+    this_block = step >= 0 ? run_block(step, input, last_output) : 0
+
+    9.downto(1) do |next_input|
+      solution = find_solution(step + 1, next_input, this_block)
+      return input.to_s + solution if solution
+    end
+    nil
+  end
+
+  memoize :find_solution
+
+  def find_max
+    find_solution(-1, 0, 0)[1..]
+  end
+end
+
+instructions = File.read('24.input').lines.map(&:strip)
+
+monad = MONAD.new(instructions)
+
+print monad.find_max, "\n"

24-2.rb

@@ -0,0 +1,72 @@
+#!/usr/bin/env ruby
+
+require 'memoist'  # https://github.com/matthewrudy/memoist
+
+class MONAD
+  extend Memoist
+
+  @@instruction_format = /^(?<inst>inp|add|mul|div|mod|eql) (?<reg>[w-z])($| (?<oper>([w-z]|[[:digit:]\-]+)))/
+
+  def initialize(program)
+    # A program is 14 blocks of almost the same 18 instructions, with
+    # three operands changing between them, on line 4 (div z), 5 (add
+    # x), and 15 (add y).
+    @divz = []
+    @addx = []
+    @addy = []
+    program.each_with_index do |insn, number|
+      @@instruction_format.match(insn) do |m|
+        if number % 18 == 4
+          @divz.append m['oper'].to_i
+        elsif number % 18 == 5
+          @addx.append m['oper'].to_i
+        elsif number % 18 == 15
+          @addy.append m['oper'].to_i
+        end
+      end
+    end
+  end
+
+  def run_block(step, w, z)
+    x = z % 26 + @addx[step]
+    z = (z / @divz[step].to_f).truncate
+    if x != w
+      z *= 26
+      z += w + @addy[step]
+    end
+    z
+  end
+
+  def find_solution(step, input, last_output)
+    return '' if step == 14 and last_output.zero?
+    return nil if step == 14
+
+    this_block = step >= 0 ? run_block(step, input, last_output) : 0
+
+    1.upto(9) do |next_input|
+      solution = find_solution(step + 1, next_input, this_block)
+      return input.to_s + solution if solution
+    end
+    nil
+  end
+
+  memoize :find_solution
+
+  def find_max
+    find_solution(-1, 0, 0)[1..]
+  end
+
+  def to_s
+    "<#{self.class}:\ndiv z: #{@divz}\nadd x: #{@addx}\nadd y: #{@addy}\n>"
+  end
+
+  def inspect
+    to_s
+  end
+end
+
+instructions = File.read('24.input').lines.map(&:strip)
+
+monad = MONAD.new(instructions)
+
+print monad.find_max, "\n"