Codility challenge

codility.rb

class Solution
  attr_reader :array  # => nil
  def initialize(a)
    @array = a        # => [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5], [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5], [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5], [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]
  end

  def peak?(left, center, right)
    left < center && center > right  # => true, false, true, false, true, false, false, false, false, true, false, true, false, false, false, false, true, false, false, false, false, true, false, true, false, true, false, true, false, false, false, false, true, false, true, false, false, false, false, true, false, false, false, true, false, true, false, true, false, false, false, false, true, false, true, false, false, false, false, true, false, false, false
  end

  def peaks
    @peaks ||= (array.each_with_index.map do |val, index|                         # => #<Enumerator: [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]:each_with_index>, #<Enumerator: [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]:each_with_index>, #<Enumerator: [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]:each_with_index>, #<Enumerator: [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]:each_with_index>, #<Enumerator: [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]:each_with_index>, #<Enumerator: [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]:each_with_index>
                  unless index == 0 || index == array.length - 1                  # => true, false, false, false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false, false, false, false, false, true
                    index if peak?(array[index-1], array[index], array[index+1])  # => 1, nil, 3, nil, 5, nil, nil, nil, nil, 10, nil, 2, nil, nil, nil, nil, 7, nil, nil, nil, 1, nil, 3, nil, 5, nil, nil, nil, nil, 10, nil, 2, nil, nil, nil, nil, 7, nil, nil, nil, 1, nil, 3, nil, 5, nil, nil, nil, nil, 10, nil, 2, nil, nil, nil, nil, 7, nil, nil, nil
                  end                                                             # => nil, 1, nil, 3, nil, 5, nil, nil, nil, nil, 10, nil, nil, nil, 2, nil, nil, nil, nil, 7, nil, nil, nil, nil, nil, 1, nil, 3, nil, 5, nil, nil, nil, nil, 10, nil, nil, nil, 2, nil, nil, nil, nil, 7, nil, nil, nil, nil, nil, 1, nil, 3, nil, 5, nil, nil, nil, nil, 10, nil, nil, nil, 2, nil, nil, nil, nil, 7, nil, nil, nil, nil
                end).select {|el| !el.nil?}                                       # => [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [2, 7], [2, 7], [2, 7], [2, 7], [2, 7], [2, 7], [2, 7], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [2, 7], [2, 7], [2, 7], [2, 7], [2, 7], [2, 7], [2, 7], [1, 3, 5, 10], [2, 7]
  end

  def can_set_flags?(nr)
    return false if peaks.length < nr            # => false, false, false, false, false, false, false, false, false, false, true, false, false, true
    
    last_index = peaks[0]                        # => 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2
    sum = 1                                      # => 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
    peaks.each_with_index do |val, index|        # => [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [2, 7], [2, 7], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [2, 7], [2, 7]
      if index != 0 && (val - last_index) >= nr  # => false, true, true, true, false, true, true, true, false, false, true, true, false, false, true, true, false, true, false, true, false, true, true, true, false, true, true, true, false, false, true, true, false, false, true, true, false, true, false, true
        last_index = val                         # => 3, 5, 10, 3, 5, 10, 5, 10, 5, 10, 7, 7, 3, 5, 10, 3, 5, 10, 5, 10, 5, 10, 7, 7
        sum += 1                                 # => 2, 3, 4, 2, 3, 4, 2, 3, 2, 3, 2, 2, 2, 3, 4, 2, 3, 4, 2, 3, 2, 3, 2, 2
      end                                        # => nil, 2, 3, 4, nil, 2, 3, 4, nil, nil, 2, 3, nil, nil, 2, 3, nil, 2, nil, 2, nil, 2, 3, 4, nil, 2, 3, 4, nil, nil, 2, 3, nil, nil, 2, 3, nil, 2, nil, 2
    end                                          # => [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [2, 7], [2, 7], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [1, 3, 5, 10], [2, 7], [2, 7]
    sum >= nr                                    # => true, true, true, false, true, true, true, true, true, false, true, true
  end

  def solve
    (1..peaks.length).lazy.map {|nr| can_set_flags?(nr)}.take_while { |can| can }.count  # => 3, 2
    # sum = 0                                                           # => 0, 0
    # (1..peaks.length).lazy.map {|nr| can_set_flags?(nr)}.each do |x|  # => #<Enumerator::Lazy: #<Enumerator::Lazy: 1..4>:map>, #<Enumerator::Lazy: #<Enumerator::Lazy: 1..2>:map>
    #   x ? sum += 1 : break                                            # => 1, 2, 3, 1, 2
    # end                                                               # => nil, nil
    # sum                                                               # => 3, 2
  end
end

def solution(a)
  Solution.new(a).solve
end

require "minitest/autorun"  # => true

class TestSolution < Minitest::Test
  attr_reader :solution, :bsolution  # => nil
  def setup
    a = [1,5,3,4,3,4,1,2,3,4,6,2]    # => [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2], [1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]
    b = [4,5,8,5,1,4,6,8,7,2,2,5]    # => [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5], [4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]
    @solution = Solution.new(a)      # => #<Solution:0x007fd6f211fca8 @array=[1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]>, #<Solution:0x007fd6f2145ca0 @array=[1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]>, #<Solution:0x007fd6f214e238 @array=[1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]>, #<Solution:0x007fd6f216d958 @array=[1, 5, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2]>
    @bsolution = Solution.new(b)     # => #<Solution:0x007fd6f211f140 @array=[4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]>, #<Solution:0x007fd6f2145610 @array=[4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]>, #<Solution:0x007fd6f214db80 @array=[4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]>, #<Solution:0x007fd6f216d138 @array=[4, 5, 8, 5, 1, 4, 6, 8, 7, 2, 2, 5]>
  end

  def test_peak
    assert_equal false, solution.peak?(2,3,4)     # => true
    assert_equal true, solution.peak?(2,3,1)      # => true
    assert_equal false, solution.peak?(52,22,14)  # => true
  end

  def test_peaks
    assert_equal [1,3,5,10], solution.peaks  # => true
    assert_equal [2,7], bsolution.peaks      # => true
  end

  def test_if_can_set_flags_on_peaks
    assert solution.can_set_flags?(1)  # => true
    assert solution.can_set_flags?(2)  # => true
    assert solution.can_set_flags?(3)  # => true
    refute solution.can_set_flags?(4)  # => false
    refute solution.can_set_flags?(5)  # => false

    assert bsolution.can_set_flags?(1)  # => true
    assert bsolution.can_set_flags?(2)  # => true
    refute bsolution.can_set_flags?(3)  # => false
  end

  def test_solve
    assert_equal 3, solution.solve   # => true
    assert_equal 2, bsolution.solve  # => true
  end
end

# >> Run options: --seed 41341
# >> 
# >> # Running:
# >> 
# >> ....
# >> 
# >> Finished in 0.003378s, 1184.1326 runs/s, 4440.4973 assertions/s.
# >> 
# >> 4 runs, 15 assertions, 0 failures, 0 errors, 0 skips