1 files changed, 173 insertions, 0 deletions
diff --git a/23/1.lua b/23/1.lua
new file mode 100644
index 0000000..b3f570f
--- /dev/null
+++ b/23/1.lua
@@ -0,0 +1,173 @@
+require "ext"
+local map = {}
+local row, col = 0,0
+local function fmt_location(row, col)
+	return string.format("%d,%d",row,col)
+end
+for line in io.lines() do
+	row = row + 1
+	col = 0
+	for char in line:gmatch("(.)") do
+		col = col + 1
+		local locf = fmt_location(row,col)
+		if char == "#" then
+			map[locf] = true
+		end
+	end
+end
+
+local directions = {
+	N = {-1,0},
+	S = {1,0},
+	E = {0,1},
+	W = {0,-1},
+	NE = {-1,1},
+	NW = {-1,-1},
+	SE = {1,1},
+	SW = {1,-1}
+}
+local dir_order = {
+	{"N","NE","NW"},
+	{"S","SE","SW"},
+	{"W","NW","SW"},
+	{"E","NE","SE"}
+}
+
+print(map)
+
+local function parse_location(location)
+	local trow,tcol = location:match("([%d-]+),([%d-]+)")
+	return tonumber(trow), tonumber(tcol)
+end
+local function round(map, order_dir)
+	--print("Directions:",order_dir)
+	--first half, propose
+	local propositions = {}
+	for location, elf in pairs(map) do
+		local elf_nearby = false
+		local trow, tcol = parse_location(location)
+		for _, dir in pairs(directions) do
+			local nrow, ncol = trow + dir[1], tcol + dir[2]
+			local nloc = fmt_location(nrow,ncol)
+			if map[nloc] then
+				elf_nearby = true
+				break
+			end
+		end
+		if not elf_nearby then
+			propositions[location] = {location}
+			goto nextelf
+		end
+		assert(elf_nearby)
+		for _,dset in ipairs(dir_order) do
+			local dir_empty = true
+			for _,d in ipairs(dset) do
+				local dir = directions[d]
+				local nrow, ncol = trow + dir[1], tcol + dir[2]
+				local nloc = fmt_location(nrow,ncol)
+				if map[nloc] then
+					dir_empty = false
+					break
+				end
+			end
+			if dir_empty then
+				local dir = directions[dset[1]]
+				local nrow, ncol = trow + dir[1], tcol + dir[2]
+				local nloc = fmt_location(nrow,ncol)
+				if not propositions[nloc] then
+					propositions[nloc] = {location}
+				else
+					table.insert(propositions[nloc],location)
+				end
+				goto nextelf
+			end
+		end
+		-- no new location proposed, sit tight
+		propositions[location] = {location}
+		::nextelf::
+	end
+
+	--print("Propositions:",propositions)
+	--second half, move if we were the only ones that want to go there
+	local any_moved = false
+	for location, elftbl in pairs(propositions) do
+		if #elftbl == 1 and elftbl[1] ~= location then
+			any_moved = true
+		end
+	end
+	if not any_moved then
+		os.exit(0)
+	end
+	local newmap = {}
+	for location, elftbl in pairs(propositions) do
+		if #elftbl == 1 then
+			newmap[location] = true
+		else
+			for _,oloc in pairs(elftbl) do
+				newmap[oloc] = true
+			end
+		end
+	end
+	return newmap
+end
+
+local function aabb(map)
+	local minrow,mincol,maxrow,maxcol= math.huge, math.huge, -math.huge, -math.huge
+	for location,_ in pairs(map) do
+		local row,col = parse_location(location)
+		minrow = math.min(minrow,row)
+		maxrow = math.max(maxrow,row)
+		mincol = math.min(mincol,col)
+		maxcol = math.max(maxcol,col)
+	end
+	return minrow, mincol, maxrow, maxcol
+end
+
+local function print_puzzle(map)
+	local minrow, mincol, maxrow, maxcol = aabb(map)
+	io.write("    ")
+	for col = mincol - 1, maxcol + 1 do
+		io.write(col)
+	end
+	io.write("\n")
+	for row = minrow - 1, maxrow + 1 do
+		io.write(string.format("%3d|",row))
+		for col = mincol - 1,maxcol + 1 do
+			local loc = fmt_location(row,col)
+			if map[loc] then
+				io.write("#")
+			else
+				io.write(".")
+			end
+		end
+		io.write("\n")
+	end
+end
+
+local function emptyaabb(map)
+	local minrow, mincol, maxrow, maxcol = aabb(map)
+	local count = 0
+	for row = minrow, maxrow do
+		for col = mincol ,maxcol do
+			local loc = fmt_location(row,col)
+			if not map[loc] then
+				count = count + 1
+			end
+		end
+	end
+	return count
+end
+
+print_puzzle(map)
+print("==========")
+local i = 0
+while true do
+	i = i + 1
+	print(i)
+	map = round(map,dir_order)
+	table.insert(dir_order,table.remove(dir_order,1))
+
+	--print_puzzle(map)
+	--print("==========")
+end
+print(emptyaabb(map))