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2025/Day8/Day8.lua

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+-- Advent of Code 2025 - Day 8 - Bas Grolleman
+require("functions")
+
+-- Variables
+local boxes = {}
+local inputfile = "Day8/test"
+local limit = 11
+
+function distance(p1, p2)
+	return math.sqrt((p2.x - p1.x) ^ 2 + (p2.y - p1.y) ^ 2 + (p2.z - p1.z) ^ 2)
+end
+function boxes.find(id)
+	for i, box in ipairs(boxes) do
+		if box.id == id then
+			return box
+		end
+	end
+end
+
+local id_counter = 0
+for line in io.lines(inputfile) do
+	local x, y, z = line:match("(%d+)%,(%d+)%,(%d+)")
+	id_counter = id_counter + 1
+	local box = {
+		id = id_counter,
+		x = tonumber(x),
+		y = tonumber(y),
+		z = tonumber(z),
+		xyz = x .. "," .. y .. "," .. z,
+	}
+	table.insert(boxes, box)
+end
+
+local distance_table = {}
+for i, box1 in ipairs(boxes) do
+	for j, box2 in ipairs(boxes) do
+		if box1.id ~= box2.id then
+			table.insert(distance_table, {
+				id1 = box1.id,
+				id2 = box2.id,
+				d = distance(box1, box2),
+			})
+		end
+	end
+end
+table.sort(distance_table, function(a, b)
+	return a.d < b.d
+end)
+
+local circuit = 0
+for i, dt in ipairs(distance_table) do
+	box1 = boxes.find(dt.id1)
+	box2 = boxes.find(dt.id2)
+	if limit > 0 then
+		io.write(string.format("%2d Linking %2d <-> %2d %.0f", limit, box1.id, box2.id, dt.d))
+		if box1.c == nil and box2.c == nil then
+			circuit = circuit + 1
+			box1.c = circuit
+			box2.c = circuit
+			limit = limit - 1
+			print(" C=" .. circuit .. " BOTH")
+		elseif box1.c ~= nil and box2.c ~= nil then
+			if box1.c == box2.c then
+				print(" C=" .. box1.c .. " ALREADY")
+			else
+				-- Oh look, we merge 2 circuits!
+				print(" Merging " .. box1.c .. " and " .. box2.c)
+				local remove = box2.c
+				for k, uc in ipairs(boxes) do
+					if uc.c == remove then
+						uc.c = box1.c
+					end
+				end
+				limit = limit - 1
+			end
+		elseif box1.c == nil then
+			box1.c = box2.c
+			limit = limit - 1
+			print(" C=" .. box1.c .. " HOOK BOX1")
+		elseif box2.c == nil then
+			box2.c = box1.c
+			limit = limit - 1
+			print(" C=" .. box1.c .. " HOOK BOX2")
+		end
+	end
+end
+for k, box in ipairs(boxes) do
+	if box.c == nil then
+		circuit = circuit + 1
+		box.c = circuit
+	end
+end
+table.sort(boxes, function(a, b)
+	return a.c < b.c
+end)
+
+local lc = 0
+local circuit_size = {}
+
+for k, box in ipairs(boxes) do
+	if lc ~= box.c then
+		circuit_size[box.c] = 1
+		print()
+	else
+		circuit_size[box.c] = circuit_size[box.c] + 1
+	end
+	print(string.format("Box %2d Circuit %2d", box.id, box.c))
+	lc = box.c
+end
+
+print()
+local circuit_size2 = {}
+for k, v in pairs(circuit_size) do
+	circuit_size2[#circuit_size2 + 1] = v
+end
+table.sort(circuit_size2, function(a, b)
+	return b < a
+end)
+print_table(circuit_size2)
+local total = circuit_size2[1] * circuit_size2[2] * circuit_size2[3]
+print("Total size " .. total)