in reply to http://challenge.greplin.com

greplin-challenge-level-1.rb

require "pp"

class String
  def all_substrings
    substrs = []
    start_index, end_index = [0, self.length - 1]
    start_index.upto end_index do |i|
      i.upto end_index do |j|
        # puts "#{self}[#{i}, #{j}] => #{ss}"
        substrs << self[i..j]
      end
    end
    substrs.uniq!
  end
end

def find_reversed_substring(word)
  # pp "#{word} => #{word.all_substrings.join(',')}"
  count = 0
  @data = Hash.new do |h, sub|
    h[sub] = []
  end

  word.all_substrings.each do |substr|
    count += 1 
    next if substr.length <= 1
    # puts "Testing #{substr} [count: #{count}]" # if count < 100
    next unless palindrome? substr
    @data[substr.length] << substr
  end
  pp @data
end

def palindrome?(string)
  string == string.reverse
end

text = <<EOF
FourscoreandsevenyearsagoourfaathersbroughtforthonthiscontainentanewnationconceivedinzLibertyanddedicatedtothepropositionthatallmenarecreatedequalNowweareengagedinagreahtcivilwartestingwhetherthatnaptionoranynartionsoconceivedandsodedicatedcanlongendureWeareqmetonagreatbattlefiemldoftzhatwarWehavecometodedicpateaportionofthatfieldasafinalrestingplaceforthosewhoheregavetheirlivesthatthatnationmightliveItisaltogetherfangandproperthatweshoulddothisButinalargersensewecannotdedicatewecannotconsecratewecannothallowthisgroundThebravelmenlivinganddeadwhostruggledherehaveconsecrateditfaraboveourpoorponwertoaddordetractTgheworldadswfilllittlenotlenorlongrememberwhatwesayherebutitcanneverforgetwhattheydidhereItisforusthelivingrathertobededicatedheretotheulnfinishedworkwhichtheywhofoughtherehavethusfarsonoblyadvancedItisratherforustobeherededicatedtothegreattdafskremainingbeforeusthatfromthesehonoreddeadwetakeincreaseddevotiontothatcauseforwhichtheygavethelastpfullmeasureofdevotionthatweherehighlyresolvethatthesedeadshallnothavediedinvainthatthisnationunsderGodshallhaveanewbirthoffreedomandthatgovernmentofthepeoplebythepeopleforthepeopleshallnotperishfromtheearth
EOF

# test
# text = <<EOF
# broughtracecarforthmalayalamtest
# EOF

words = text.gsub(/\s+/, ' ').gsub(/[^\w\s]/, '').split(' ')
words.each do |w|
  puts "Checking word #{w}"
  find_reversed_substring w
end

greplin-challenge-level-3.rb

require "set"

class Array
  def sum
    inject { |sum, n| sum += n }
  end
end

def find_sub_arrays(nums)
  selected_sub_arrays = Set.new
  nums.sort!
  puts "Whole thing: #{nums.inspect}"
  0.upto(nums.size - 1) do |i|
    (i).upto(nums.size - 1) do |j|
      nums.combination(j).each do |sub_arr|
        next if sub_arr.empty? or selected_sub_arrays.member? sub_arr
        if candidate_array? sub_arr
          puts "#{sub_arr.inspect} works! (current count: #{selected_sub_arrays.size + 1})"
          selected_sub_arrays << sub_arr
        end
      end
    end
  end
  selected_sub_arrays
end

def candidate_array?(arr)
  # the array is already sorted
  array = arr.dup
  largest = array.pop
  array.sum == largest ? true : false
end

nums = [ 3, 4, 9, 14, 15, 19, 28, 37, 47, 50, 54, 56, 59, 61, 70, 73, 78, 81, 92, 95, 97, 99 ]
# nums = [ 1, 2, 3, 4, 6 ]

puts "answer: #{find_sub_arrays(nums).size}"

greplin-challenge-level2.rb

require "pp"

def next_fibonacci(start_num, end_num)
  start_num + end_num
end

def find_fibonacci_after(prev_num, next_num, lower_bound)
  next_fib = next_fibonacci(prev_num, next_num)

  if ( next_fib >= lower_bound ) && ( prime? next_fib )
    puts " ==========> found! #{next_fib} <============"
  else
    puts "Looking for the next fib after: #{next_fib}"
    find_fibonacci_after(next_num, next_fib, lower_bound)
  end
end

@known_primes = [2]
def prime?(num)
  # rand(100) > 80 ? true : false
  (2..num/2).each do |i|
    return false if num % i == 0
  end
  true
end

lower_bound = 217000
find_fibonacci_after(1, 2, lower_bound)

# 514229
# 2 + 3 + 5 + 61 + 281 = 352
# 2 * 3 * 5 * 61 * 281 = 514230