1823 - Find the Winner of the Circular Game

Mix.install([])

ExUnit.start(auto_run: false)

Solution

https://leetcode.com/problems/find-the-winner-of-the-circular-game

defmodule Solution do
  @spec find_the_winner(n :: integer, k :: integer) :: integer
  def find_the_winner(n, k) do
    do_find_the_winner(Enum.to_list(1..n), n, k, _pos = 0)
  end

  defp do_find_the_winner(_circle = [winner], _n, _k, _pos), do: winner

  defp do_find_the_winner(circle, n, k, pos) do
    split_index = rem(k + pos - 1, n)

    circle = List.delete_at(circle, split_index)
    do_find_the_winner(circle, n - 1, k, split_index)
  end
end

defmodule TestSolution do
  use ExUnit.Case, async: false

  test "1" do
    assert Solution.find_the_winner(5, 2) == 3
  end

  test "2" do
    assert Solution.find_the_winner(6, 5) == 1
  end
end

ExUnit.run()