solved part 2

day09/solution2.rb

@@ -0,0 +1,41 @@
+#!/bin/env ruby
+
+def valid_nums (nums)
+    nums.map { |num| nums
+        .map { |sub| sub + num if sub != num }}.flatten.uniq.compact
+end
+
+def find_invalid (numbers, preamble)
+    numbers.each.with_index do |number, i|
+        next if i < preamble
+        if !valid_nums(numbers[(i-preamble)..(i-1)]).include?(number)
+            return i, number
+            break
+        end
+    end
+end
+numbers = File.readlines('./input').to_ary.map(&:strip!).map(&:to_i)
+preamble = 25
+
+index, wrong_number = find_invalid(numbers, preamble)
+
+pp index, wrong_number
+numbers.slice!(index..)
+numbers.delete_if { |number| number > wrong_number }
+
+max = numbers.length
+step = 1
+solution = nil
+while step < max do
+    range_sums = numbers.map.with_index { |num, i| {"#{i..i+step}" => numbers[i..i+step].sum}}
+    range_sums.each do |set|
+        if set.values.include?(wrong_number)
+            solution = set
+            break
+        end
+    end
+    step += 1
+end
+first, last = solution.keys[0].split('..').map(&:to_i)
+pp solution
+p numbers[first..last].min + numbers[first..last].max