Lychrel numbers: Difference between revisions

=={{header|Crystal}}==

{{trans|Ruby}}

<lang ruby>require "set"

require "big"

def add_reverse(num, max_iter=1000)

num = num.to_big_i

nums = [] of BigInt

(1..max_iter).each_with_object(Set.new([num])) do |_, nums|

num += reverse_int(num)

nums << num

return nums if palindrome?(num)

end

end

def palindrome?(num)

num == reverse_int(num)

end

def reverse_int(num)

num.to_s.reverse.to_big_i

end

def split_roots_from_relateds(roots_and_relateds)

roots = roots_and_relateds.dup

i = 1

while i < roots.size

this = roots[i]

if roots[0...i].any?{ |prev| this.intersects?(prev) }

roots.delete_at(i)

else

i += 1

end

end

root = roots.map{|each_set| each_set.min}

related = roots_and_relateds.map{|each_set| each_set.min}

related = related.reject{|n| root.includes?(n)}

return root, related

end

def find_lychrel(maxn, max_reversions)

series = (1..maxn).map{|n| add_reverse(n, max_reversions*2)}

roots_and_relateds = series.select{|s| s.size > max_reversions}

split_roots_from_relateds(roots_and_relateds)

end

maxn, reversion_limit = 10000, 500

puts "Calculations using n = 1..#{maxn} and limiting each search to 2*#{reversion_limit} reverse-digits-and-adds"

lychrel, l_related = find_lychrel(maxn, reversion_limit)

puts " Number of Lychrel numbers: #{lychrel.size}"

puts " Lychrel numbers: #{lychrel}"

puts " Number of Lychrel related: #{l_related.size}"

pals = (lychrel + l_related).select{|x| palindrome?(x)}.sort

puts " Number of Lychrel palindromes: #{pals.size}"

puts " Lychrel palindromes: #{pals}"</lang>

{{out}}

<pre>

Calculations using n = 1..10000 and limiting each search to 2*500 reverse-digits-and-adds

Number of Lychrel numbers: 5

Lychrel numbers: [196, 879, 1997, 7059, 9999]

Number of Lychrel related: 244

Number of Lychrel palindromes: 3

Lychrel palindromes: [4994, 8778, 9999]

</pre>