2025aoc3.lua

function joltage(line, n)
  local index = 1
  local result = 0
  for a = 1, n do
    local maxDigit = line:byte(index)
    for i = index, #line - (n - a) do
      if line:byte(i) > maxDigit then
        maxDigit = line:byte(i)
        index = i
      end
    end
    result = result * 10 + (maxDigit - 48)
    index = index + 1
  end
  return result
end

local result1 = 0
local result2 = 0
for line in io.lines("input.txt", "l") do
  result1 = result1 + joltage(line, 2)
  result2 = result2 + joltage(line, 12)
end

print(result1)
print(result2)