2 files changed, 42 insertions(+), 1 deletions(-)

A 2023/15.lua
M 2023/Makefile

@@ 0,0 1,41 @@
+io.input(arg[1])
+local line = io.read()
+local function hash(s)
+	local h = 0
+	for i = 1, #s do
+		h = ((h + string.byte(s, i)) * 17) & 0xff
+	end
+	return h
+end
+local map, ans1, ans2 = {}, 0, 0
+for step, label, op, val in line:gmatch('((%a+)([-=])(%d*))') do
+	ans1 = ans1 + hash(step)
+	local h = hash(label)
+	local box = map[h]
+	if not box then box = {} map[h] = box end
+	if op == '-' then
+		for i, t in ipairs(box) do
+			if t[1] == label then
+				table.remove(box, i)
+				break
+			end
+		end
+	else
+		local found
+		for i, t in ipairs(box) do
+			if t[1] == label then
+				t[2] = val
+				found = true
+			end
+		end
+		if not found then
+			table.insert(box, {label, val})
+		end
+	end
+end
+for i, box in pairs(map) do
+	for j, t in ipairs(box) do
+		ans2 = ans2 + (i + 1) * j * t[2]
+	end
+end
+print(ans1, ans2)

@@ 4,7 4,7 @@
 LUA?=lua
 
 .PHONY: all
-all: 1 2 3 4 5 6 7 9 10 11 13 14
+all: 1 2 3 4 5 6 7 9 10 11 13 14 15
 
 .DEFAULT:
 	@printf 'day %s\t' $< && $(LUA) $<.lua < $<.txt