day1.rb

require_relative "spec_helper"

def count_increases(nums)
  nums.each_cons(2).to_a.count do |window|
    window[0] < window[1]
  end
end

def sum_by_window(nums)
  nums.each_cons(3).map do |window|
    window.sum
  end
end

def read_nums_from_string(string)
  string.split("\n").map(&:to_i)
end

# puts count_increases(File.read("day1_input.txt"))
# puts count_increases(sum_by_window(read_nums_from_string(File.read("day1_input.txt"))))

RSpec.describe "Day 1" do
  let(:example) do
    <<~INPUT
      199
      200
      208
      210
      200
      207
      240
      269
      260
      263
    INPUT
  end

  describe "#sum_by_window" do
    it "works" do
      expect(sum_by_window([1, 2, 3, 4])).to eql [1 + 2 + 3, 2 + 3 + 4]
    end
  end

  specify "part 1 - example" do
    expect(count_increases(read_nums_from_string(example))).to eql 7
  end

  specify "part 1 - answer" do
    expect(count_increases(read_nums_from_string(File.read("day1_input.txt")))).to eql 1624
  end

  specify "part 1 - one liner answer" do
    expect(File.read("day1_input.txt").lines.map(&:to_i).each_cons(2).count { _1 < _2 }).to eql 1624
  end

  specify "part 2 - example" do
    expect(count_increases(sum_by_window(read_nums_from_string(example)))).to eql 5
  end

  specify "part 2 - answer" do
    expect(count_increases(sum_by_window(read_nums_from_string(File.read("day1_input.txt"))))).to eql 1653
  end

  specify "part 2 - one liner answer" do
    expect(File.read("day1_input.txt").lines.map(&:to_i).each_cons(3).map { _1.sum }.each_cons(2).count { _1 < _2 }).to eql 1653
  end
end