problem 51 solution

ruby/euler.rb

@@ -64,5 +64,13 @@ module Euler
       true
     end
 
+    def non_empty_subsets(list)
+      (1..list.count).map { |x| list.combination(x).to_a }.flatten(1)
+    end
+
+    def powerset(list)
+      (0..list.count).map { |x| list.combination(x).to_a }.flatten(1)
+    end
+
   end
 end

ruby/euler051.rb

@@ -1,28 +1,61 @@
-def permutations?(number_list)
+require_relative 'euler'
-  comparison_digit_list = to_digit_list(number_list.first).sort
+
-  number_list.all? { |x| to_digit_list(x).sort == comparison_digit_list }
+# i = 0
+# Prime.take_while do |p|
+#   i += 1
+#   result = false
+#   digits = p.to_digit_list
+#   Euler.non_empty_subsets(digits).each do |index_list|
+#     related_primes = []
+#     ('1'..'9').each do |j|
+#       copied_digit_list = Array.new(digits)
+#       index_list.each do |index|
+#         copied_digit_list[index] = j
+#       end
+#       new_num = Euler.from_digit_list(copied_digit_list)
+#       related_primes.push(new_num) if new_num.prime? and !related_primes.include?(new_num)
+#     end
+#     if related_primes.count == 7
+#       puts p
+#       puts '---'
+#       puts related_primes.inspect
+#       result = related_primes
+#     end
+#   end
+#   puts result if i % 1000
+#   result == false
+# end
+
+def bitmasks(length)
+  (1..2**length-1).map { |n| n.to_s(2) }.map { |s| s.rjust(4, '0')}.map { |s| s.split('').map(&:to_i)}
 end
 
-def six_multiples(x)
+def prime_digit_replacement(number, mask)
-  [x, 2 * x, 3 * x, 4 * x, 5 * x, 6 * x]
+  digits = number.to_digit_list
+  related_primes = []
+  ('0'..'9').each do |j|
+    copied_digit_list = Array.new(digits)
+    mask.each_with_index do |bit, index|
+      copied_digit_list[index] = j if bit == 1
+    end
+    new_num = Euler.from_digit_list(copied_digit_list)
+    related_primes.push(new_num) if new_num.prime? and !related_primes.include?(new_num) and new_num.to_digit_list.count == digits.count
+  end
+  related_primes
 end
 
-def infinite_series
+def solution(family_count)
-  Enumerator.new do |y|
+  result = false
-    n = 1
+  Prime.take_while do |p|
-    loop do
+    digits = p.to_digit_list
-      y << n
+    bitmasks(digits.count).each do |mask|
-      n += 1
+      related_primes = prime_digit_replacement(p, mask)
+      if related_primes.count == family_count and related_primes.include?(p)
+        result = p
+        break
       end
     end
+    result == false
   end
-
+  result
-def same_digit_six_multiples
-  series = infinite_series
-  n = series.next
-  loop do
-    result = permutations?(six_multiples(n))
-    return six_multiples(n) if result
-    n = series.next
-  end
 end

ruby/euler052.rb

@@ -0,0 +1,28 @@
+def permutations?(number_list)
+  comparison_digit_list = to_digit_list(number_list.first).sort
+  number_list.all? { |x| to_digit_list(x).sort == comparison_digit_list }
+end
+
+def six_multiples(x)
+  [x, 2 * x, 3 * x, 4 * x, 5 * x, 6 * x]
+end
+
+def infinite_series
+  Enumerator.new do |y|
+    n = 1
+    loop do
+      y << n
+      n += 1
+    end
+  end
+end
+
+def same_digit_six_multiples
+  series = infinite_series
+  n = series.next
+  loop do
+    result = permutations?(six_multiples(n))
+    return six_multiples(n) if result
+    n = series.next
+  end
+end