pascals_triangle

elixir/pascals-triangle/.exercism/config.json

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+{
+  "authors": [
+    "dalexj"
+  ],
+  "contributors": [
+    "amencarini",
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "devonestes",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "sotojuan",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/pascals_triangle.ex"
+    ],
+    "test": [
+      "test/pascals_triangle_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Compute Pascal's triangle up to a given number of rows.",
+  "source": "Pascal's Triangle at Wolfram Math World",
+  "source_url": "https://www.wolframalpha.com/input/?i=Pascal%27s+triangle"
+}

elixir/pascals-triangle/.exercism/metadata.json

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+{"track":"elixir","exercise":"pascals-triangle","id":"71d888253d44412db03d365e545aa233","url":"https://exercism.org/tracks/elixir/exercises/pascals-triangle","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/pascals-triangle/.formatter.exs

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

elixir/pascals-triangle/.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").
+pascals_triangle-*.tar
+

elixir/pascals-triangle/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/pascals_triangle.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/pascals-triangle/README.md

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+# Pascal's Triangle
+
+Welcome to Pascal's Triangle on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Compute Pascal's triangle up to a given number of rows.
+
+In Pascal's Triangle each number is computed by adding the numbers to the right and left of the current position in the previous row.
+
+```text
+    1
+   1 1
+  1 2 1
+ 1 3 3 1
+1 4 6 4 1
+# ... etc
+```
+
+## Source
+
+### Created by
+
+- @dalexj
+
+### Contributed to by
+
+- @amencarini
+- @angelikatyborska
+- @Cohen-Carlisle
+- @devonestes
+- @lpil
+- @neenjaw
+- @parkerl
+- @sotojuan
+- @waiting-for-dev
+
+### Based on
+
+Pascal's Triangle at Wolfram Math World - https://www.wolframalpha.com/input/?i=Pascal%27s+triangle

elixir/pascals-triangle/lib/pascals_triangle.ex

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+defmodule PascalsTriangle do
+  @doc """
+  Calculates the rows of a pascal triangle
+  with the given height
+  """
+  @spec rows(integer) :: [[integer]]
+  def rows(num) do
+    1..num
+    |> Enum.reduce([[]], fn _, triangle -> [next(hd(triangle)) | triangle] end)
+    |> Enum.take(num)
+    |> Enum.reverse
+  end
+
+  defp next(from, acc \\ [])
+  defp next([], _acc), do: [1]
+  defp next([1], _acc), do: [1, 1]
+  defp next([one, two | []], acc), do: [1 | Enum.reverse([1, one + two | acc])]
+  defp next([one, two | rest], acc), do: next([two | rest], [one + two | acc])
+end

elixir/pascals-triangle/mix.exs

@@ -0,0 +1,28 @@
+defmodule PascalsTriangle.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :pascals_triangle,
+      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/pascals-triangle/test/pascals_triangle_test.exs

@@ -0,0 +1,152 @@
+defmodule PascalsTriangleTest do
+  use ExUnit.Case
+
+  test "one row" do
+    assert PascalsTriangle.rows(1) == [[1]]
+  end
+
+  test "two rows" do
+    assert PascalsTriangle.rows(2) == [[1], [1, 1]]
+  end
+
+  test "three rows" do
+    assert PascalsTriangle.rows(3) == [[1], [1, 1], [1, 2, 1]]
+  end
+
+  test "four rows" do
+    assert PascalsTriangle.rows(4) == [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1]]
+  end
+
+  test "five rows" do
+    assert PascalsTriangle.rows(5) == [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1], [1, 4, 6, 4, 1]]
+  end
+
+  test "six rows" do
+    assert PascalsTriangle.rows(6) == [
+             [1],
+             [1, 1],
+             [1, 2, 1],
+             [1, 3, 3, 1],
+             [1, 4, 6, 4, 1],
+             [1, 5, 10, 10, 5, 1]
+           ]
+  end
+
+  test "ten rows" do
+    assert PascalsTriangle.rows(10) == [
+             [1],
+             [1, 1],
+             [1, 2, 1],
+             [1, 3, 3, 1],
+             [1, 4, 6, 4, 1],
+             [1, 5, 10, 10, 5, 1],
+             [1, 6, 15, 20, 15, 6, 1],
+             [1, 7, 21, 35, 35, 21, 7, 1],
+             [1, 8, 28, 56, 70, 56, 28, 8, 1],
+             [1, 9, 36, 84, 126, 126, 84, 36, 9, 1]
+           ]
+  end
+
+  test "20 rows" do
+    assert PascalsTriangle.rows(20) == [
+             [1],
+             [1, 1],
+             [1, 2, 1],
+             [1, 3, 3, 1],
+             [1, 4, 6, 4, 1],
+             [1, 5, 10, 10, 5, 1],
+             [1, 6, 15, 20, 15, 6, 1],
+             [1, 7, 21, 35, 35, 21, 7, 1],
+             [1, 8, 28, 56, 70, 56, 28, 8, 1],
+             [1, 9, 36, 84, 126, 126, 84, 36, 9, 1],
+             [1, 10, 45, 120, 210, 252, 210, 120, 45, 10, 1],
+             [1, 11, 55, 165, 330, 462, 462, 330, 165, 55, 11, 1],
+             [1, 12, 66, 220, 495, 792, 924, 792, 495, 220, 66, 12, 1],
+             [1, 13, 78, 286, 715, 1287, 1716, 1716, 1287, 715, 286, 78, 13, 1],
+             [1, 14, 91, 364, 1001, 2002, 3003, 3432, 3003, 2002, 1001, 364, 91, 14, 1],
+             [1, 15, 105, 455, 1365, 3003, 5005, 6435, 6435, 5005, 3003, 1365, 455, 105, 15, 1],
+             [
+               1,
+               16,
+               120,
+               560,
+               1820,
+               4368,
+               8008,
+               11440,
+               12870,
+               11440,
+               8008,
+               4368,
+               1820,
+               560,
+               120,
+               16,
+               1
+             ],
+             [
+               1,
+               17,
+               136,
+               680,
+               2380,
+               6188,
+               12376,
+               19448,
+               24310,
+               24310,
+               19448,
+               12376,
+               6188,
+               2380,
+               680,
+               136,
+               17,
+               1
+             ],
+             [
+               1,
+               18,
+               153,
+               816,
+               3060,
+               8568,
+               18564,
+               31824,
+               43758,
+               48620,
+               43758,
+               31824,
+               18564,
+               8568,
+               3060,
+               816,
+               153,
+               18,
+               1
+             ],
+             [
+               1,
+               19,
+               171,
+               969,
+               3876,
+               11628,
+               27132,
+               50388,
+               75582,
+               92378,
+               92378,
+               75582,
+               50388,
+               27132,
+               11628,
+               3876,
+               969,
+               171,
+               19,
+               1
+             ]
+           ]
+  end
+end

elixir/pascals-triangle/test/test_helper.exs

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