1232 - Check If It Is a Straight Line

Mix.install([])

ExUnit.start(auto_run: false)

Solution

https://leetcode.com/problems/check-if-it-is-a-straight-line

defmodule Solution do
  @spec check_straight_line(coordinates :: [[integer]]) :: boolean
  def check_straight_line(coordinates) do
    [[x1, y1], [x2, y2] | coordinates] = coordinates

    cond do
      x1 == x2 ->
        Enum.all?(coordinates, fn [x, _y] -> x == x1 end)

      true ->
        a = (y1 - y2) / (x1 - x2)
        b = y1 - a * x1

        Enum.all?(coordinates, fn [x, y] -> y == a * x + b end)
    end
  end
end

defmodule TestSolution do
  use ExUnit.Case, async: false

  test "1" do
    assert Solution.check_straight_line([[1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7]]) == true
  end

  test "2" do
    assert Solution.check_straight_line([[0, 0], [0, 1], [0, -1]]) == true
  end
end

ExUnit.run()