day 14

day14/part1.lua

@@ -0,0 +1,51 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local file = io.open(arg[3])
+local prevchar = nil
+local paircounts = {}
+for char in chars(file:read("*l")) do
+	if prevchar ~= nil then 
+		paircounts[prevchar..char] = (paircounts[prevchar..char] or 0) + 1
+	end
+	prevchar = char
+end
+
+file:read("*l") -- skip empty line
+local line = file:read("*l")
+local rules = {}
+while line ~= nil do
+	rules[char(line, 1)..char(line, 2)] = char(line, 7)
+	line = file:read("*l")
+end
+
+for step = 1, 10 do
+	local npaircounts = {}
+	for pair, count in pairs(paircounts) do
+		if rules[pair] then
+			local p1, p2 = char(pair, 1)..rules[pair], rules[pair]..char(pair, 2)
+			npaircounts[p1] = (npaircounts[p1] or 0) + count
+			npaircounts[p2] = (npaircounts[p2] or 0) + count
+		else
+			npaircounts[pair] = (npaircounts[pair] or 0) + count
+		end
+	end
+	paircounts = npaircounts
+	printtable(paircounts)
+end
+
+local charcounts = {}
+for pair, count in pairs(paircounts) do
+	charcounts[char(pair, 1)] = (charcounts[char(pair, 1)] or 0) + count
+	charcounts[char(pair, 2)] = (charcounts[char(pair, 2)] or 0) + count
+end
+foreach(charcounts, function(v) return math.ceil(v / 2) end)
+printtable(charcounts)
+
+local min, max = math.huge, 0
+for char, count in pairs(charcounts) do
+	if count < min then min = count end
+	if count > max then max = count end
+end
+
+print(max - min)

day14/part2.lua

@@ -0,0 +1,51 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local file = io.open(arg[3])
+local prevchar = nil
+local paircounts = {}
+for char in chars(file:read("*l")) do
+	if prevchar ~= nil then 
+		paircounts[prevchar..char] = (paircounts[prevchar..char] or 0) + 1
+	end
+	prevchar = char
+end
+
+file:read("*l") -- skip empty line
+local line = file:read("*l")
+local rules = {}
+while line ~= nil do
+	rules[char(line, 1)..char(line, 2)] = char(line, 7)
+	line = file:read("*l")
+end
+
+for step = 1, 40 do
+	local npaircounts = {}
+	for pair, count in pairs(paircounts) do
+		if rules[pair] then
+			local p1, p2 = char(pair, 1)..rules[pair], rules[pair]..char(pair, 2)
+			npaircounts[p1] = (npaircounts[p1] or 0) + count
+			npaircounts[p2] = (npaircounts[p2] or 0) + count
+		else
+			npaircounts[pair] = (npaircounts[pair] or 0) + count
+		end
+	end
+	paircounts = npaircounts
+	printtable(paircounts)
+end
+
+local charcounts = {}
+for pair, count in pairs(paircounts) do
+	charcounts[char(pair, 1)] = (charcounts[char(pair, 1)] or 0) + count
+	charcounts[char(pair, 2)] = (charcounts[char(pair, 2)] or 0) + count
+end
+foreach(charcounts, function(v) return math.ceil(v / 2) end)
+printtable(charcounts)
+
+local min, max = math.huge, 0
+for char, count in pairs(charcounts) do
+	if count < min then min = count end
+	if count > max then max = count end
+end
+
+print(max - min)