Day 03

4 files changed, 340 insertions, 0 deletions

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 @@
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