leetcode: solve two sum problem in elixir

leetcode/0001-two-sum/elixir/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

leetcode/0001-two-sum/elixir/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+two_sum-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

leetcode/0001-two-sum/elixir/lib/two_sum.ex

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+defmodule Solution do
+  @spec two_sum(nums :: [integer], target :: integer) :: [integer]
+  def two_sum(nums, target) do
+    process_num(nums, target)
+  end
+
+  @spec process_num(
+          nums :: [integer],
+          target :: integer,
+          head_idx :: integer,
+          indexes :: %{integer => integer}
+        ) :: [integer]
+  defp process_num([head | tail], target, head_idx \\ 0, indexes \\ %{}) do
+    first_idx = indexes[target - head]
+
+    if first_idx != nil do
+      [first_idx, head_idx]
+    else
+      indexes = Map.put(indexes, head, head_idx)
+      process_num(tail, target, head_idx + 1, indexes)
+    end
+  end
+end

leetcode/0001-two-sum/elixir/mix.exs

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+defmodule TwoSum.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :two_sum,
+      version: "0.1.0",
+      elixir: "~> 1.16",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

leetcode/0001-two-sum/elixir/test/test_helper.exs

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+ExUnit.start()

leetcode/0001-two-sum/elixir/test/two_sum_test.exs

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+defmodule SolutionTest do
+  use ExUnit.Case
+  doctest Solution
+
+  test "example 1" do
+    assert Solution.two_sum([2, 7, 11, 15], 9) == [0, 1]
+  end
+
+  test "example 2" do
+    assert Solution.two_sum([3, 2, 4], 6) == [1, 2]
+  end
+
+  test "example 3" do
+    assert Solution.two_sum([3, 3], 6) == [0, 1]
+  end
+end