Kata Training

Challenges

Two Sums

Write a function that takes an array of numbers (integers for the tests) and a target number. It should find two different items in the array that, when added together, give the target value. The indexes of these items should then be returned in a tuple / list like: {index1, index2}.

Example input: ([1, 2, 3], 4) Output: {0, 2}

defmodule TwoSums do
  @moduledoc false
  # ([2,3,4,5,8], 11)

  def get_addends(numbers, target) do
    numbers
    |> Enum.with_index()
    |> Enum.reduce_while(%{}, fn {val, idx}, seen ->
      complement = target - val

      if is_map_key(seen, complement) do
        {:halt, {seen[complement], idx}}
      else
        {:cont, Map.put(seen, val, idx)}
      end
    end)
    
  end
end

TwoSums.get_addends([1,2,3], 4)

Commands (wip)

Write a function that parses a list that contains 3 items: ["ADD", a, b] first argument is the command to process, the others 2 are the arguments(integers) for that operation.

Example input: ["ADD", 2, 3] Output: 5

defmodule Commands do
  @moduledoc false

  def parse_command(payload) do
    payload
    |> List.to_tuple()
  end
end

Commands.parse_command(["ADD", 2, 4])