Partition function P: Difference between revisions
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Took 131ms</pre>
=={{header|Elixir}}==
Loosely based on the Erlang version.
<lang Elixir>
use Bitwise, skip_operators: true
defmodule Partition do
def init(), do:
:ets.new :pN, [:set, :named_table, :private]
def gpentagonals(), do: Stream.unfold {1, 0}, &next/1
defp next({m, n}) do
a = case rem m, 2 do
0 -> div m, 2
1 -> m
end
{n, {m + 1, n + a}}
end
def p(0), do: 1
def p(n) do
case :ets.lookup :pN, n do
[{^n, val}] -> val
[] ->
{val, _} = gpentagonals()
|> Stream.drop(1)
|> Stream.take_while(fn m -> m <= n end)
|> Stream.map(fn g -> p(n - g) end)
|> Enum.reduce({0, 0},
fn n, {a, sgn} -> {
a + (if sgn < 2, do: n, else: -n),
band(sgn + 1, 3)
}
end)
:ets.insert :pN, {n, val}
val
end
end
end
Partition.init
IO.puts Partition.p 6666
</lang>
{{Out}}
<pre>
193655306161707661080005073394486091998480950338405932486880600467114423441282418165863
</pre>
=={{header|Erlang}}==
<lang Erlang>
Line 295 ⟶ 341:
sys 0m0.080s
</pre>
=={{header|F_Sharp|F#}}==
An implementation of the formula in the task description. P(123456) is included for comparison with the largest value in the related task.
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