I’m new to Elixir (started yesterday) and as a first little program, I wanted to solve the Münchausen numbers problem.
“A Münchausen number is a number equal to the sum of its digits raised to each digit’s power. For instance, 3435 is a Münchausen number because 3^3+4^4+3^3+5^5 = 3435. The largest Münchausen number is less than 440 million.”
The problem is that my program eats up all my RAM (16 GB) and the OS kills the process. And I don’t understand what goes on with the garbage collector.
Here is my solution:
#!/usr/bin/env elixir
defmodule Munchausen do
@cache [0] ++ for n <- 1..9, do: n ** n
def get_cache(), do: @cache
def explode(n), do: explode(n, [])
# int, acc -> list[int]
def explode(n, acc) when n == 0, do: acc
def explode(n, acc) do
digit = rem(n, 10)
explode(div(n, 10), [digit | acc])
end
# int -> bool
def is_munchausen(n) do
digits = explode(n)
li = for x <- digits, do: Enum.at(@cache, x)
n == Enum.sum(li)
end
end
defmodule Main do
# @max 10_000
@max 440_000_000
def main() do
# Munchausen.get_cache() |> IO.inspect
for n <- 0..@max do
# :erlang.garbage_collect()
if rem(n, 1_000_000) == 0 do
IO.puts("# #{n}")
end
if Munchausen.is_munchausen(n) do
IO.puts(n)
end
end
end
end
Main.main()
I know that it’s not optimal and slow. I’ll work on it.
Now the question is: why does it consume all my memory and how to prevent that? Thanks.