day 11

day11/part1.lua

@@ -0,0 +1,56 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local grid = {}
+for line in io.lines(arg[3]) do
+	local row = {}
+	for char in chars(line) do
+		table.insert(row, tonumber(char))
+	end
+	table.insert(grid, row)
+end
+
+function printgrid()
+	for r, row in pairs(grid) do
+		for c, cell in pairs(row) do
+			if cell > 9 then
+				io.write('*')
+			else
+				io.write(cell)
+			end
+		end
+		io.write('\n')
+	end
+end
+
+printgrid()
+
+function flash(grid, r, c)
+	grid[r][c] = grid[r][c] + 1
+	if grid[r][c] == 10 then 
+		for dr = -1, 1 do if 0 < r + dr and r + dr <= #grid then
+			for dc = -1, 1 do if 0 < c + dc and c + dc <= #grid[r] then
+				flash(grid, r + dr, c + dc)
+			end end
+		end end
+	end
+end
+
+local flashes = 0
+for step = 1, 100 do
+	for r, row in pairs(grid) do
+		for c, cell in pairs(row) do
+			flash(grid, r, c)
+		end
+	end
+	for r, row in pairs(grid) do
+		for c, cell in pairs(row) do
+			if cell > 9 then
+				grid[r][c] = 0
+				flashes = flashes + 1
+			end
+		end
+	end
+	print(flashes)
+	printgrid()
+end

day11/part2.lua

@@ -0,0 +1,60 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local grid = {}
+for line in io.lines(arg[3]) do
+	local row = {}
+	for char in chars(line) do
+		table.insert(row, tonumber(char))
+	end
+	table.insert(grid, row)
+end
+
+function printgrid()
+	for r, row in pairs(grid) do
+		for c, cell in pairs(row) do
+			if cell > 9 then
+				io.write('*')
+			else
+				io.write(cell)
+			end
+		end
+		io.write('\n')
+	end
+end
+
+printgrid()
+
+function flash(grid, r, c)
+	grid[r][c] = grid[r][c] + 1
+	if grid[r][c] == 10 then 
+		for dr = -1, 1 do if 0 < r + dr and r + dr <= #grid then
+			for dc = -1, 1 do if 0 < c + dc and c + dc <= #grid[r] then
+				flash(grid, r + dr, c + dc)
+			end end
+		end end
+	end
+end
+
+for step = 1, math.huge do
+	for r, row in pairs(grid) do
+		for c, cell in pairs(row) do
+			flash(grid, r, c)
+		end
+	end
+	local flashes = 0
+	for r, row in pairs(grid) do
+		for c, cell in pairs(row) do
+			if cell > 9 then
+				grid[r][c] = 0
+				flashes = flashes + 1
+			end
+		end
+	end
+	print(flashes)
+	printgrid()
+	if flashes == #grid * #grid[1] then
+		print(step)
+		break
+	end
+end