From 61713a5faad8fad679639a2ed8e8a305a8e22603 Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Sun, 6 Dec 2020 21:35:13 -0800
Subject: [PATCH] Add say 7 solution.

---
 day7.cr | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 day7.cr

diff --git a/day7.cr b/day7.cr
new file mode 100644
index 0000000..6329e2f
--- /dev/null
+++ b/day7.cr
@@ -0,0 +1,44 @@
+require "advent"
+
+INPUT = input(2020, 7).lines.map(&.chomp).map do |s|
+  data = s.match(/^([a-z ]+) bags contain (.*).$/).not_nil!
+  {data[1], data[2].split(", ").map(&.rchop(" bags").rchop(" bag")) }
+end
+
+def build_graph(input)
+  gr = Graph(String).new
+  seen = Set(String).new
+  input.each do |i|
+    next if i[1] == ["no other"]
+    seen << i[0]
+    i[1].each do |to|
+      n, _, m = to.partition(" ")
+      n = n.to_i32
+      gr.add_edge(i[0], m, n)
+    end
+  end
+  {seen, gr}
+end
+
+def part1
+  seen, gr = build_graph(INPUT)
+  seen.count do |s|
+    gr.find_path(s, "shiny gold") && s != "shiny gold"
+  end
+end
+
+def count_bags(gr, current)
+  return 1 unless es = gr.@edges[current]?
+  1 + es.sum do |e|
+    t, k = e
+    k * count_bags(gr, t)
+  end
+end
+
+def part2
+  seen, gr = build_graph(INPUT)
+  count_bags(gr, "shiny gold") - 1
+end
+
+puts part1
+puts part2