tasks a-s

Task/Self-referential-sequence/Ruby/self-referential-sequence.rb

@@ -0,0 +1,37 @@
+$cache = {}
+def selfReferentialSequence_cached(n, seen = [])
+  return $cache[n] if $cache.include? n
+  return [] if seen.include? n
+
+  digit_count = Array.new(10, 0)
+  n.to_s.chars.collect {|char| digit_count[char.to_i] += 1}
+  term = ''
+  9.downto(0).each do |d|
+    if digit_count[d] > 0
+      term += digit_count[d].to_s + d.to_s
+    end
+  end
+  term = term.to_i
+  $cache[n] = [n] + selfReferentialSequence_cached(term, [n] + seen)
+end
+
+limit = 1_000_000
+max_len = 0
+max_vals = []
+
+1.upto(limit - 1) do |n|
+  seq = selfReferentialSequence_cached(n)
+  if seq.length > max_len
+    max_len = seq.length
+    max_vals = [n]
+  elsif seq.length == max_len
+    max_vals << n
+  end
+end
+
+puts "values: #{max_vals.inspect}"
+puts "iterations: #{max_len}"
+puts "sequence:"
+selfReferentialSequence_cached(max_vals[0]).each_with_index do |val, idx|
+  puts "%2d %d" % [idx + 1, val]
+end