From c62e6e28ad065948557aea88958631462a42b1ec Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Sat, 3 Dec 2022 16:32:03 +0000
Subject: Day 03

---
 day03/input    | 300 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 day03/part1.rb |  19 ++++
 day03/part2.rb |  15 +++
 day03/test     |   6 ++
 4 files changed, 340 insertions(+)
 create mode 100644 day03/input
 create mode 100644 day03/part1.rb
 create mode 100644 day03/part2.rb
 create mode 100644 day03/test

diff --git a/day03/input b/day03/input
new file mode 100644
index 0000000..cd857ef
--- /dev/null
+++ b/day03/input
@@ -0,0 +1,300 @@
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diff --git a/day03/part1.rb b/day03/part1.rb
new file mode 100644
index 0000000..0ae732b
--- /dev/null
+++ b/day03/part1.rb
@@ -0,0 +1,19 @@
+def priority(ch)
+  if ch >= ?a && ch <= ?z
+    ch.ord - 96
+  elsif ch >= ?A && ch <= ?Z
+    ch.ord - 64 + 26
+  end
+end
+
+backpacks = $stdin.readlines.map do |line|
+  line = line.strip
+  half = line.length / 2
+  [line[0...half].chars, line[half..-1].chars]
+end
+
+commons = backpacks.map do |f, s|
+  (f & s)[0]
+end
+
+puts commons.map{|ch|priority(ch)}.sum
diff --git a/day03/part2.rb b/day03/part2.rb
new file mode 100644
index 0000000..baaecb9
--- /dev/null
+++ b/day03/part2.rb
@@ -0,0 +1,15 @@
+def priority(ch)
+  if ch >= ?a && ch <= ?z
+    ch.ord - 96
+  elsif ch >= ?A && ch <= ?Z
+    ch.ord - 64 + 26
+  end
+end
+
+backpacks = $stdin.readlines.map(&:strip).map(&:chars)
+
+commons = backpacks.each_slice(3).map do |backpacks|
+  backpacks.inject(:&)[0]
+end
+
+puts commons.map{|ch|priority(ch)}.sum
diff --git a/day03/test b/day03/test
new file mode 100644
index 0000000..f17e726
--- /dev/null
+++ b/day03/test
@@ -0,0 +1,6 @@
+vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw
-- 
cgit v1.2.1