Add solution for 2015 day 17 part 1

2015/day-17/inputs/puzzle.txt

@@ -0,0 +1,20 @@
+11
+30
+47
+31
+32
+36
+3
+1
+5
+3
+32
+36
+15
+11
+46
+26
+28
+1
+19
+3

2015/day-17/inputs/test.txt

@@ -0,0 +1,5 @@
+20
+5
+15
+10
+5

2015/day-17/main.rb

@@ -0,0 +1,44 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "pathname"
+require "set"
+
+Container = Struct.new(:id, :cap)
+
+# quite inefficient, probably needs a DP solution
+def combinations(amount, containers, stack = [], results = Set[])
+  stack_sum = stack.sum { |x| x.cap }
+
+  if stack_sum > amount
+    return results
+  elsif stack_sum == amount
+    results.add(stack.dup)
+    return results
+  end
+
+  return results if containers.empty?
+
+  containers.each_with_index do |container, idx|
+    combinations(amount, containers[(idx+1)..], [*stack, container], results)
+  end
+
+  combinations(amount, containers[1..], [], results)
+end
+
+def main(amount, file_paths)
+  amount = amount.to_i
+
+  file_paths.each do |file_path|
+    puts "Files: #{file_path}"
+
+    containers = file_path.each_line.with_index.map { |x, i| Container.new(i, x.to_i) }.freeze
+
+    result = combinations(amount, containers)
+
+    solution1 = result.size
+    puts "  Solution 1: #{solution1}"
+  end
+end
+
+main(ARGV[0], ARGV[1..].map { |x| Pathname(x) })