2023 Day 9 Part 1 Complete

2023/09/Guardfile

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+#guard :shell do
+#  watch(%r{^*\.rb}) { `bundle exec rspec --force-color -f doc spec/ ` }
+#end
+
+guard 'rspec', cmd: 'bundle exec rspec --force-color -f doc spec/', :all_on_start => true do
+  watch(%r{^([^/]+)\.rb$}) { |m| "spec/#{m[1]}_spec.rb" }
+  watch(%r{^spec/.*_spec\.rb$})
+end
+
+notification :tmux,
+  display_message: true,
+  timeout: 5, # in seconds
+  default_message_format: '%s >> %s',
+  success:                "green",
+  failed:                 "red",
+  pending:                "yellow",
+  default:                "green"

2023/09/run.rb

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+#!/usr/bin/env ruby
+
+require_relative 'sequences'
+
+input = File.read('./input.txt')
+
+ad = Advent::Sequences.new(input)
+puts "Part 1 Sum: #{ad.sum_next_number}"

2023/09/sequences.rb

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+require 'set'
+require '../lib/grid.rb'
+require '../lib/ring.rb'
+
+module Advent
+
+  class Sequences
+    attr_accessor :debug
+    attr_reader :sequences
+
+    def initialize(input)
+      @debug = false
+      @sequences = input.lines.map do |line|
+        line.split.map(&:to_i)
+      end
+    end
+
+    def debug!
+      @debug = true
+    end
+
+    def diffs(sequence)
+      sequence.each_cons(2).map do |a, b|
+        b - a
+      end 
+    end
+
+    def next_number(sequence)
+      working = [sequence.dup]
+      puts "Working A: #{working.inspect}" if @debug
+      until working.last.all?(&:zero?) do
+        working << diffs(working.last)
+        puts "Working B: #{working.inspect}" if @debug
+      end
+
+      while working.length > 1 do
+        puts "Working C: #{working.inspect}" if @debug
+        seq = working.pop
+        working.last << working.last.last + seq.last
+      end
+
+      puts "Working D: #{working.inspect}" if @debug
+      working.last.last
+    end
+
+    def sum_next_number
+      @sequences.sum do |seq|
+        next_number(seq)
+      end
+    end
+  end
+end

2023/09/spec/sequences_spec.rb

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+require './sequences.rb'
+require 'rspec'
+require 'pry'
+
+describe Advent do
+
+  let(:input) {
+    <<~EOS
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45
+    EOS
+  }
+
+  describe Advent::Sequences do
+    let(:ad) { Advent::Sequences.new(input) }
+
+    describe "#new" do
+      it "inits sequences" do
+        expect(ad.sequences).to eq([
+          [0, 3, 6, 9, 12, 15],
+          [1, 3, 6, 10, 15, 21],
+          [10, 13, 16, 21, 30, 45],
+        ])
+      end
+    end
+
+    describe "#next_number" do
+      it "returns the next number in the sequence" do
+        # ad.debug!
+        expect(ad.next_number([0, 3, 6, 9, 12, 15])).to eq(18)
+        expect(ad.next_number([1, 3, 6, 10, 15, 21])).to eq(28)
+        expect(ad.next_number([10, 13, 16, 21, 30, 45])).to eq(68)
+      end
+    end
+
+    context "validation" do
+
+      it "returns the sum of the next number in the sequence for part 1" do
+        expect(ad.sum_next_number).to eq(114)
+      end
+    end
+  end
+end