adventofcode-2021/day04/part1.lua

#!/usr/bin/env luajit

function split(text, sep)
	local parts = {}
	local start = 0
	local from, to = text:find(sep)
	while from ~= nil do
		table.insert(parts, text:sub(start, from - 1))
		text = text:sub(to + 1)
		from, to = text:find(sep)
	end
	table.insert(parts, text)
	return parts
end

local f = io.open(arg[3])
local numbers = split(f:read("*l"), ",")
local line = f:read("*l")
local boards = {}
while line ~= nil do
	local board = {}
	for r = 1, 5 do
		line = f:read("*l")
		while line:byte(1) == string.byte(" ", 1) do
			line = line:sub(2)
		end
		board[r] = split(line, " +")
	end
	table.insert(boards, board)
	line = f:read("*l")
end

local i, complete = 0, nil
while complete == nil and i <= #numbers do
	local number = numbers[i]
	local tests = {}
	for b, board in pairs(boards) do
		for r, row in pairs(board) do
			for c, col in pairs(row) do
				if col == number then
					row[c] = nil
					table.insert(tests, {b, r, c})
				end
			end
		end
	end

	for t, test in pairs(tests) do
		local board, row, col = unpack(test)
		local j, rownils, colnils = 1, 0, 0
		while j <= 5 and (rownils == 0 or colnils == 0) do
			if boards[board][row][j] ~= nil then rownils = rownils + 1 end
			if boards[board][j][col] ~= nil then colnils = colnils + 1 end
			j = j + 1
		end
		if rownils == 0 or colnils == 0 then
			complete = boards[board]
		end
	end

	i = i + 1
end

print(numbers[i - 1])
local sum = 0
for r = 1, 5 do
	for c = 1, 5 do
		io.write((complete[r][c] or "nil") .. " ")
		sum = sum + (complete[r][c] or 0)
	end
	io.write("\n")
end
print(numbers[i - 1] * sum)