From a80aa90a8b47a3e6be04a4ee1ebb11b3dd29494f Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Sat, 8 Dec 2018 17:36:38 +0000
Subject: [day08] done

---
 day08/part2 | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100755 day08/part2

(limited to 'day08/part2')

diff --git a/day08/part2 b/day08/part2
new file mode 100755
index 0000000..94c2415
--- /dev/null
+++ b/day08/part2
@@ -0,0 +1,36 @@
+#!/usr/bin/env ruby
+
+def parse_tree(input, start)
+  num_children = input[start]
+  num_metadata = input[start + 1]
+
+  children = []
+  next_index = start + 2
+  while num_children > 0 do
+    sum, endindex = parse_tree(input, next_index)
+    children << sum
+    next_index = endindex + 1
+    num_children -= 1
+  end
+
+  value = 0
+  if children.empty?
+    while num_metadata > 0 do
+      value += input[next_index]
+      next_index += 1
+      num_metadata -= 1
+    end
+  else
+    while num_metadata > 0 do
+      i = input[next_index]
+      value += children[i - 1] if i <= children.length
+      next_index += 1
+      num_metadata -= 1
+    end
+  end
+  return [ value, next_index - 1 ]
+end
+
+input = gets.chomp.split.map(&:to_i)
+
+puts parse_tree(input, 0)[0]
-- 
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