Exercises

.ruby-version

2.0.0-p247

frog_spec.rb

class Solver
  def self.solution(x, y, d)
    ( (y - x) * 1.0 / d).ceil
  end
end

describe Solver do

  specify do
    expect(Solver.solution 10, 85 ,30).to eq 3
  end
  specify do
    expect(Solver.solution 10, 10 ,30).to eq 0
  end
end

Gemfile

source 'http://rubygems.org'

gem 'rspec'

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    diff-lcs (1.2.4)
    rspec (2.14.1)
      rspec-core (~> 2.14.0)
      rspec-expectations (~> 2.14.0)
      rspec-mocks (~> 2.14.0)
    rspec-core (2.14.7)
    rspec-expectations (2.14.3)
      diff-lcs (>= 1.1.3, < 2.0)
    rspec-mocks (2.14.4)

PLATFORMS
  ruby

DEPENDENCIES
  rspec

peaks_spec.rb

class Peaks
  def initialize mountains
    @mountains = mountains
    @peaks = []
  end

  def peaks_number
    @mountains.size.times do |index|
      @peaks << index if is_peak?(index)
    end
    @peaks
  end

  def is_peak?(index)
    @mountains[index - 1] <  @mountains[index] &&
      @mountains[index + 1] < @mountains[index]
  end

  def max_flags
    peaks_number
    result = 0
    (1..@peaks.size).to_a.each do |max_flag_n|
      achieved_flags = @peaks.reduce([@peaks.first]) do |flags_ary, flag|
        flag - flags_ary.last >= max_flag_n &&
          flags_ary.push(flag) || flags_ary
      end
      result = max_flag_n if max_flag_n <= achieved_flags.size
    end
    result
  end
end

describe Peaks do
  let(:example) { [1,5,3,4,3,4,1,2,3,4,6,2] }

  subject do
    Peaks.new example
  end

  it 'should find the max number of flags' do
    expect(subject.max_flags).to eq 3
  end

  specify do
    expect(subject.peaks_number).to eq [1, 3, 5, 10]
  end

  it 'should find the peaks' do
    expect(subject.is_peak? 1).to be_true
    expect(subject.is_peak? 2).to be_false
  end
end

tape_spec.rb

class Tape
  def self.solution(a)

    p1 = a[0]
    p2 = a[1...a.length].reduce(&:+)
    (1...a.length).map do |index|
      p1 += a[index]
      p2 -= a[index]
      (p1 - p2).abs

    end.sort.first
  end
end

describe Tape do
  let(:example) { [3,1,2,4,3] }
  let(:example2) { [1,1,1,1,1,1] }
  let(:example3) do
    Array.new(1_000_000).tap do |ary|
      ary.map! {|n| rand n }
    end
  end

  specify do
    expect(Tape.solution(example)).to eq 1
  end

  specify do
    expect(Tape.solution(example2)).to eq 0
  end
  specify do
    expect(Tape.solution(example3)).to eq 0
  end
end