binary_search_tree

elixir/binary-search-tree/.exercism/config.json

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+{
+  "authors": [
+    "sngeth"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "devonestes",
+    "neenjaw",
+    "sotojuan"
+  ],
+  "files": {
+    "solution": [
+      "lib/binary_search_tree.ex"
+    ],
+    "test": [
+      "test/binary_search_tree_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Insert and search for numbers in a binary tree.",
+  "source": "Josh Cheek"
+}

elixir/binary-search-tree/.exercism/metadata.json

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+{"track":"elixir","exercise":"binary-search-tree","id":"fc6ed3ee9f82408eb78d0f9df5e506bf","url":"https://exercism.org/tracks/elixir/exercises/binary-search-tree","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/binary-search-tree/.formatter.exs

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

elixir/binary-search-tree/.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").
+binary_search_tree-*.tar
+

elixir/binary-search-tree/HELP.md

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+# Help
+
+## Running the tests
+
+From the terminal, change to the base directory of the exercise then execute the tests with:
+
+```bash
+$ mix test
+```
+
+This will execute the test file found in the `test` subfolder -- a file ending in `_test.exs`
+
+Documentation:
+
+* [`mix test` - Elixir's test execution tool](https://hexdocs.pm/mix/Mix.Tasks.Test.html)
+* [`ExUnit` - Elixir's unit test library](https://hexdocs.pm/ex_unit/ExUnit.html)
+
+## Pending tests
+
+In test suites of practice exercises, all but the first test have been tagged to be skipped.
+
+Once you get a test passing, you can unskip the next one by commenting out the relevant `@tag :pending` with a `#` symbol.
+
+For example:
+
+```elixir
+# @tag :pending
+test "shouting" do
+  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
+end
+```
+
+If you wish to run all tests at once, you can include all skipped test by using the `--include` flag on the `mix test` command:
+
+```bash
+$ mix test --include pending
+```
+
+Or, you can enable all the tests by commenting out the `ExUnit.configure` line in the file `test/test_helper.exs`.
+
+```elixir
+# ExUnit.configure(exclude: :pending, trace: true)
+```
+
+## Useful `mix test` options
+
+* `test/<FILE>.exs:LINENUM` - runs only a single test, the test from `<FILE>.exs` whose definition is on line `LINENUM`
+* `--failed` - runs only tests that failed the last time they ran
+* `--max-failures` - the suite stops evaluating tests when this number of test failures
+is reached
+* `--seed 0` - disables randomization so the tests in a single file will always be ran
+in the same order they were defined in
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit lib/binary_search_tree.ex` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Elixir track's documentation](https://exercism.org/docs/tracks/elixir)
+- The [Elixir track's programming category on the forum](https://forum.exercism.org/c/programming/elixir)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+If you're stuck on something, it may help to look at some of the [available resources](https://exercism.org/docs/tracks/elixir/resources) out there where answers might be found.

elixir/binary-search-tree/README.md

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+# Binary Search Tree
+
+Welcome to Binary Search Tree on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Insert and search for numbers in a binary tree.
+
+When we need to represent sorted data, an array does not make a good data structure.
+
+Say we have the array `[1, 3, 4, 5]`, and we add 2 to it so it becomes `[1, 3, 4, 5, 2]`.
+Now we must sort the entire array again!
+We can improve on this by realizing that we only need to make space for the new item `[1, nil, 3, 4, 5]`, and then adding the item in the space we added.
+But this still requires us to shift many elements down by one.
+
+Binary Search Trees, however, can operate on sorted data much more efficiently.
+
+A binary search tree consists of a series of connected nodes.
+Each node contains a piece of data (e.g. the number 3), a variable named `left`, and a variable named `right`.
+The `left` and `right` variables point at `nil`, or other nodes.
+Since these other nodes in turn have other nodes beneath them, we say that the left and right variables are pointing at subtrees.
+All data in the left subtree is less than or equal to the current node's data, and all data in the right subtree is greater than the current node's data.
+
+For example, if we had a node containing the data 4, and we added the data 2, our tree would look like this:
+
+      4
+     /
+    2
+
+If we then added 6, it would look like this:
+
+      4
+     / \
+    2   6
+
+If we then added 3, it would look like this
+
+       4
+     /   \
+    2     6
+     \
+      3
+
+And if we then added 1, 5, and 7, it would look like this
+
+          4
+        /   \
+       /     \
+      2       6
+     / \     / \
+    1   3   5   7
+
+## Source
+
+### Created by
+
+- @sngeth
+
+### Contributed to by
+
+- @angelikatyborska
+- @Cohen-Carlisle
+- @devonestes
+- @neenjaw
+- @sotojuan
+
+### Based on
+
+Josh Cheek

elixir/binary-search-tree/lib/binary_search_tree.ex

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+defmodule BinarySearchTree do
+  @type bst_node :: %{data: any, left: bst_node | nil, right: bst_node | nil}
+
+  @doc """
+  Create a new Binary Search Tree with root's value as the given 'data'
+  """
+  @spec new(any) :: bst_node
+  def new(data), do: %{data: data, left: nil, right: nil}
+
+  @doc """
+  Creates and inserts a node with its value as 'data' into the tree.
+  """
+  @spec insert(bst_node, any) :: bst_node
+  def insert(nil, data), do: new(data)
+  def insert(tree, data) when data <= tree.data, do:
+    %{tree | left: insert(tree.left, data)}
+  def insert(tree, data), do:
+    %{tree | right: insert(tree.right, data)}
+
+  @doc """
+  Traverses the Binary Search Tree in order and returns a list of each node's data.
+  """
+  @spec in_order(bst_node) :: [any]
+  def in_order(nil), do: []
+  def in_order(tree), do: in_order(tree.left) ++ [tree.data | in_order(tree.right)]
+end

elixir/binary-search-tree/mix.exs

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+defmodule BinarySearchTree.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :binary_search_tree,
+      version: "0.1.0",
+      # elixir: "~> 1.8",
+      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

elixir/binary-search-tree/test/binary_search_tree_test.exs

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+defmodule BinarySearchTreeTest do
+  use ExUnit.Case
+
+  test "data is retained" do
+    root = BinarySearchTree.new(4)
+    assert root.data == 4
+    assert root.left == nil
+    assert root.right == nil
+  end
+
+  describe "insert data at proper node" do
+    test "smaller number at left node" do
+      root =
+        BinarySearchTree.new(4)
+        |> BinarySearchTree.insert(2)
+
+      assert root.data == 4
+      assert root.left.data == 2
+      assert root.left.left == nil
+      assert root.left.right == nil
+      assert root.right == nil
+    end
+
+    test "same number at left node" do
+      root =
+        BinarySearchTree.new(4)
+        |> BinarySearchTree.insert(4)
+
+      assert root.data == 4
+      assert root.left.data == 4
+      assert root.left.left == nil
+      assert root.left.right == nil
+      assert root.right == nil
+    end
+
+    test "greater number at right node" do
+      root =
+        BinarySearchTree.new(4)
+        |> BinarySearchTree.insert(5)
+
+      assert root.data == 4
+      assert root.left == nil
+      assert root.right.data == 5
+      assert root.right.left == nil
+      assert root.right.right == nil
+    end
+  end
+
+  test "can create complex tree" do
+    root =
+      BinarySearchTree.new(4)
+      |> BinarySearchTree.insert(2)
+      |> BinarySearchTree.insert(6)
+      |> BinarySearchTree.insert(1)
+      |> BinarySearchTree.insert(3)
+      |> BinarySearchTree.insert(5)
+      |> BinarySearchTree.insert(7)
+
+    assert root.data == 4
+    assert root.left.data == 2
+    assert root.left.left.data == 1
+    assert root.left.left.left == nil
+    assert root.left.left.right == nil
+    assert root.left.right.data == 3
+    assert root.left.right.left == nil
+    assert root.left.right.right == nil
+    assert root.right.data == 6
+    assert root.right.left.data == 5
+    assert root.right.left.left == nil
+    assert root.right.left.right == nil
+    assert root.right.right.data == 7
+    assert root.right.right.left == nil
+    assert root.right.right.right == nil
+  end
+
+  describe "can sort data" do
+    test "can sort single number" do
+      root = BinarySearchTree.new(2)
+
+      assert [2] == BinarySearchTree.in_order(root)
+    end
+
+    test "can sort if second number is smaller than first" do
+      root =
+        BinarySearchTree.new(2)
+        |> BinarySearchTree.insert(1)
+
+      assert [1, 2] == BinarySearchTree.in_order(root)
+    end
+
+    test "can sort if second number is the same as the first" do
+      root =
+        BinarySearchTree.new(2)
+        |> BinarySearchTree.insert(2)
+
+      assert [2, 2] == BinarySearchTree.in_order(root)
+    end
+
+    test "can sort if second number is greater than the first" do
+      root =
+        BinarySearchTree.new(2)
+        |> BinarySearchTree.insert(3)
+
+      assert [2, 3] == BinarySearchTree.in_order(root)
+    end
+
+    test "can sort complex tree" do
+      root =
+        BinarySearchTree.new(2)
+        |> BinarySearchTree.insert(1)
+        |> BinarySearchTree.insert(3)
+        |> BinarySearchTree.insert(6)
+        |> BinarySearchTree.insert(7)
+        |> BinarySearchTree.insert(5)
+
+      assert [1, 2, 3, 5, 6, 7] == BinarySearchTree.in_order(root)
+    end
+  end
+end

elixir/binary-search-tree/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)