1 files changed, 42 insertions, 0 deletions
diff --git a/12/2.lua b/12/2.lua
new file mode 100644
index 0000000..e4f2c1f
--- /dev/null
+++ b/12/2.lua
@@ -0,0 +1,42 @@
+#!/usr/bin/env lua
+
+local heights = {}
+for i = string.byte('a'),string.byte('z') do
+	heights[string.char(i)] = i - string.byte('a')
+end
+heights.S, heights.E = heights.a, heights.z
+
+local map = {}
+local seen, unseen = {},{}
+local endpos
+for line in io.lines() do
+	map[#map+1] = {}
+	for char in line:gmatch("(.)") do
+		table.insert(map[#map],{height = heights[char], wts = math.huge})
+		if char == "S" then
+			start = {#map,#map[#map]}
+			map[#map][#map[#map]].wts = 0
+		elseif char == "E" then
+			endpos = {#map,#map[#map]}
+		elseif char == "a" then
+			table.insert(unseen, {#map,#map[#map]})
+			map[#map][#map[#map]].wts = 0
+		end
+	end
+end
+local adjacents = {{-1,0},{1,0},{0,-1},{0,1}}
+while #unseen > 0 do
+	local vertex = table.remove(unseen,1)
+	local data = map[vertex[1]][vertex[2]]
+	for _, offset in pairs(adjacents) do
+		local row,col = vertex[1] + offset[1], vertex[2] + offset[2]
+		if map[row] and map[row][col] and (map[row][col].height <= data.height + 1)  then
+			local adata = map[row][col]
+			if adata.wts > data.wts + 1 then
+				adata.wts = data.wts + 1
+				table.insert(unseen,{row,col})
+			end
+		end
+	end
+end
+print(map[endpos[1]][endpos[2]].wts)