16 lines
621 B
Elixir
16 lines
621 B
Elixir
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defmodule CollatzConjecture do
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@doc """
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calc/1 takes an integer and returns the number of steps required to get the
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number to 1 when following the rules:
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- if number is odd, multiply with 3 and add 1
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- if number is even, divide by 2
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"""
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@spec calc(input :: pos_integer()) :: non_neg_integer()
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def calc(input) when is_integer(input) and input > 0, do: collatz(input)
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defp collatz(input, steps \\ 0)
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defp collatz(1, steps), do: steps
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defp collatz(input, steps) when rem(input, 2) == 0, do: collatz(div(input, 2), steps + 1)
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defp collatz(input, steps), do: collatz(input * 3 + 1, steps + 1)
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end
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