Submission #18985752

---

Source Code Expand

defmodule Main do
  def main do
    [n, k] = IO.read(:line) |> String.trim() |> String.split(" ") |> Enum.map(&String.to_integer/1)
    list =
      1..n
      |> Enum.reduce([], fn _, acc ->
        line = IO.read(:line) |> String.trim() |> String.split(" ") |> Enum.map(&String.to_integer/1)
        [line | acc]
      end)
      |> Enum.reverse()

    solve(n, k, list) |> IO.puts()
  end

  def solve(n, k, list) do
    (0..n-1)
    |> Enum.to_list()
    |> permutations()
    |> Enum.filter(fn path -> Enum.at(path, 0) == 0 end)
    |> Enum.map(fn path ->
      (0..n-1)
      |> Enum.reduce(0, fn i, acc ->
        now_point = Enum.at(path, i)
        next_point = if i == n - 1 do 0 else Enum.at(path, i + 1) end
        acc + Enum.at(Enum.at(list, now_point), next_point)
      end)
    end)
    |> Enum.filter(&(&1 == k))
    |> Enum.count()
  end

  def permutations([]), do: [[]]
  def permutations(list), do: for elm <- list, rest <- permutations(list -- [elm]), do: [elm | rest]
end

Submission Info

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