File : pitagora.lua

--[[
// Function to reduce sum of digits to a single digit
int reduce_to_single_digit(int sum) {
    while (sum >= 10) {
        int new_sum = 0;
        while (sum > 0) {
            new_sum += sum % 10;
            sum /= 10;
        }
        sum = new_sum;
    }
    return sum;
}
]]
local function reduce_to_single_digit(sum)
  while sum >= 10 do
    local new_sum = 0
    while sum > 0 do
      new_sum = new_sum + ( sum % 10 )
      sum = math.floor( sum / 10 )
    end
    sum = new_sum
    print("new_sum : "..new_sum)
  end
  return sum
end

print( reduce_to_single_digit(108) )
print( reduce_to_single_digit(128) )