From 44936f2906632d460803fdb738f0f424149f1c00 Mon Sep 17 00:00:00 2001
From: Alpha Chen <alpha@kejadlen.dev>
Date: Sun, 11 Dec 2022 21:33:53 -0800
Subject: [PATCH] [2022][ruby][12.x]

---
 2022/ruby/day_12.rb | 69 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 2022/ruby/day_12.rb

diff --git a/2022/ruby/day_12.rb b/2022/ruby/day_12.rb
new file mode 100644
index 0000000..201c798
--- /dev/null
+++ b/2022/ruby/day_12.rb
@@ -0,0 +1,69 @@
+height_map = ARGF.read.lines(chomp: true).map(&:chars)
+  .each.with_index.with_object({}) do |(row,y),map|
+    row.each.with_index do |height,x|
+      map[[y,x]] = height
+    end
+  end
+
+s, e = height_map.invert.values_at(?S, ?E)
+height_map[s] = ?a
+height_map[e] = ?z
+
+# part one
+# queue = [s]
+# visited = { s => 0 }
+
+# until visited.has_key?(e)
+#   current = queue.shift
+#   moves = visited.fetch(current)
+
+#   neighbors = [
+#     [-1,  0],
+#     [ 1,  0],
+#     [ 0, -1],
+#     [ 0,  1],
+#   ].map { current.zip(_1).map {|a,b| a + b } }
+#     .select { height_map.has_key?(_1) }
+#     .reject { visited.has_key?(_1) }
+#     .select { height_map.fetch(_1).ord - 1 <= height_map.fetch(current).ord }
+
+#   neighbors.each do |y,x|
+#     visited[[y,x]] = moves + 1
+#     queue << [y,x]
+#   end
+
+#   queue.sort_by { visited.fetch(_1) }
+# end
+
+# p visited.fetch(e)
+
+# part two
+queue = [e]
+visited = { e => 0 }
+
+loop do
+  current = queue.shift
+  moves = visited.fetch(current)
+
+  neighbors = [
+    [-1,  0],
+    [ 1,  0],
+    [ 0, -1],
+    [ 0,  1],
+  ].map { current.zip(_1).map {|a,b| a + b } }
+    .select { height_map.has_key?(_1) }
+    .reject { visited.has_key?(_1) }
+    .select { height_map.fetch(current).ord <= height_map.fetch(_1).ord + 1 }
+
+  if a = neighbors.find { height_map.fetch(_1) == ?a }
+    p moves + 1
+    break
+  end
+
+  neighbors.each do |y,x|
+    visited[[y,x]] = moves + 1
+    queue << [y,x]
+  end
+
+  queue.sort_by { visited.fetch(_1) }
+end