5 more solutions

euler047.rb

@@ -0,0 +1,5 @@
+require 'prime'
+
+def solution_up_to(n)
+  (1..n).map { |x| Prime.prime_division(x).count }.each_cons(4).find_index { |x| x.all? { |y| y == 4} } + 1
+end

euler048.rb

@@ -0,0 +1,3 @@
+def series(n)
+  (1..n).map { |x| x ** x }.inject(:+)
+end

euler049.rb

@@ -0,0 +1,23 @@
+require 'prime'
+
+def four_digit_increasing_by(n)
+  return [] if (9999 - (2*n)) < 0
+  solutions = []
+  (1..(9999 - (2*n))).each do |x|
+    solutions << [x, x + n, x + (2 * n)]
+  end
+  solutions
+end
+
+def to_digit_list(num)
+  num.to_s.split('').map(&:to_i)
+end
+
+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 find_prime_permutations(n)
+  four_digit_increasing_by(n).select { |x| permutations?(x) }.select { |x| x.all? { |y| Prime.prime?(y) } }
+end

euler050.rb

@@ -0,0 +1,22 @@
+require 'prime'
+
+def longest_sum_of_consecutive_primes_beneath(n)
+  sum = 0
+  primes = Prime.take_while { |x| (sum += x) < n }
+  longest_prime_count = 0
+  longest_prime_sum = 0
+  prime_list = []
+  (1..primes.count).each do |x|
+    primes.each_cons(x) do |y|
+      subcount = y.inject(:+)
+      if Prime.prime?(subcount)
+        if y.count > longest_prime_count
+          longest_prime_sum = subcount
+          longest_prime_count = y.count
+          prime_list = y
+        end
+      end
+    end
+  end
+  [prime_list, longest_prime_sum]
+end

euler051.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