sum_of_multiples

elixir/sum-of-multiples/.exercism/config.json

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+{
+  "authors": [
+    "petehuang"
+  ],
+  "contributors": [
+    "andrewsardone",
+    "angelikatyborska",
+    "CoderDennis",
+    "Cohen-Carlisle",
+    "dalexj",
+    "devonestes",
+    "elasticdog",
+    "jinyeow",
+    "krishandley",
+    "kytrinyx",
+    "lpil",
+    "neenjaw",
+    "parkerl",
+    "rubysolo",
+    "sotojuan",
+    "Teapane",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/sum_of_multiples.ex"
+    ],
+    "test": [
+      "test/sum_of_multiples_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Given a number, find the sum of all the multiples of particular numbers up to but not including that number.",
+  "source": "A variation on Problem 1 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=1"
+}

elixir/sum-of-multiples/.exercism/metadata.json

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+{"track":"elixir","exercise":"sum-of-multiples","id":"3fe0813a41a1451aac780f8d7b811319","url":"https://exercism.org/tracks/elixir/exercises/sum-of-multiples","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/sum-of-multiples/.formatter.exs

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

elixir/sum-of-multiples/.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").
+sum_of_multiples-*.tar
+

elixir/sum-of-multiples/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/sum_of_multiples.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/sum-of-multiples/README.md

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+# Sum of Multiples
+
+Welcome to Sum of Multiples on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Introduction
+
+You work for a company that makes an online, fantasy-survival game.
+
+When a player finishes a level, they are awarded energy points.
+The amount of energy awarded depends on which magical items the player found while exploring that level.
+
+## Instructions
+
+Your task is to write the code that calculates the energy points that get awarded to players when they complete a level.
+
+The points awarded depend on two things:
+
+- The level (a number) that the player completed.
+- The base value of each magical item collected by the player during that level.
+
+The energy points are awarded according to the following rules:
+
+1. For each magical item, take the base value and find all the multiples of that value that are less than the level number.
+2. Combine the sets of numbers.
+3. Remove any duplicates.
+4. Calculate the sum of all the numbers that are left.
+
+Let's look at an example:
+
+**The player completed level 20 and found two magical items with base values of 3 and 5.**
+
+To calculate the energy points earned by the player, we need to find all the unique multiples of these base values that are less than level 20.
+
+- Multiples of 3 less than 20: `{3, 6, 9, 12, 15, 18}`
+- Multiples of 5 less than 20: `{5, 10, 15}`
+- Combine the sets and remove duplicates: `{3, 5, 6, 9, 10, 12, 15, 18}`
+- Sum the unique multiples: `3 + 5 + 6 + 9 + 10 + 12 + 15 + 18 = 78`
+- Therefore, the player earns **78** energy points for completing level 20 and finding the two magical items with base values of 3 and 5.
+
+## Source
+
+### Created by
+
+- @petehuang
+
+### Contributed to by
+
+- @andrewsardone
+- @angelikatyborska
+- @CoderDennis
+- @Cohen-Carlisle
+- @dalexj
+- @devonestes
+- @elasticdog
+- @jinyeow
+- @krishandley
+- @kytrinyx
+- @lpil
+- @neenjaw
+- @parkerl
+- @rubysolo
+- @sotojuan
+- @Teapane
+- @waiting-for-dev
+
+### Based on
+
+A variation on Problem 1 at Project Euler - https://projecteuler.net/problem=1

elixir/sum-of-multiples/lib/sum_of_multiples.ex

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+defmodule SumOfMultiples do
+  @doc """
+  Adds up all numbers from 1 to a given end number that are multiples of the factors provided.
+  """
+  @spec to(non_neg_integer, [non_neg_integer]) :: non_neg_integer
+  def to(limit, factors) do
+    for x <- 1..(limit - 1),
+        Enum.any?(factors, &(&1 != 0 && rem(x, &1) == 0 )),
+        reduce: 0
+    do
+      acc ->
+          IO.inspect(acc)
+          x + acc
+    end
+  end
+
+  # def to(limit, factors) do
+  #   factors
+  #   |> Enum.flat_map(&multipliers(&1, limit))
+  #   |> Enum.uniq()
+  #   |> Enum.sum()
+  # end
+
+  # defp multipliers(from, to) when from <= to and rem(to, from) == 0, do: Enum.take_every(from..(to - 1), from)
+  # defp multipliers(from, to) when from <= to, do: Enum.take_every(from..to, from)
+  # defp multipliers(_from, _to), do: []
+end

elixir/sum-of-multiples/mix.exs

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+defmodule SumOfMultiples.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :sum_of_multiples,
+      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/sum-of-multiples/test/sum_of_multiples_test.exs

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+defmodule SumOfMultiplesTest do
+  use ExUnit.Case
+
+  test "no multiples within limit" do
+    assert SumOfMultiples.to(1, [3, 5]) == 0
+  end
+
+  test "one factor has multiples within limit" do
+    assert SumOfMultiples.to(4, [3, 5]) == 3
+  end
+
+  test "more than one multiple within limit0" do
+    assert SumOfMultiples.to(7, [3]) == 9
+  end
+
+  test "more than one factor with multiples within limit" do
+    assert SumOfMultiples.to(10, [3, 5]) == 23
+  end
+
+  test "each multiple is only counted once" do
+    assert SumOfMultiples.to(100, [3, 5]) == 2318
+  end
+
+  test "a much larger limit" do
+    assert SumOfMultiples.to(1000, [3, 5]) == 233_168
+  end
+
+  test "three factors" do
+    multiples = [7, 13, 17]
+    assert SumOfMultiples.to(20, multiples) == 51
+  end
+
+  test "factors not relatively prime" do
+    multiples = [4, 6]
+    assert SumOfMultiples.to(15, multiples) == 30
+  end
+
+  test "some pairs of factors relatively prime and some not" do
+    multiples = [5, 6, 8]
+    assert SumOfMultiples.to(150, multiples) == 4419
+  end
+
+  test "one factor is a multiple of another" do
+    multiples = [5, 25]
+    assert SumOfMultiples.to(51, multiples) == 275
+  end
+
+  test "much larger factors" do
+    multiples = [43, 47]
+    assert SumOfMultiples.to(10000, multiples) == 2_203_160
+  end
+
+  test "all numbers are multiples of 1" do
+    multiples = [1]
+    assert SumOfMultiples.to(100, multiples) == 4950
+  end
+
+  test "no factors means an empty sum" do
+    multiples = []
+    assert SumOfMultiples.to(10000, multiples) == 0
+  end
+
+  test "the only multiple of 0 is 0" do
+    multiples = [0]
+    assert SumOfMultiples.to(1, multiples) == 0
+  end
+
+  test "the factor 0 does not affect the sum of multiples of other factors" do
+    multiples = [3, 0]
+    assert SumOfMultiples.to(4, multiples) == 3
+  end
+
+  test "solutions using include-exclude must extend to cardinality greater than 3" do
+    multiples = [2, 3, 5, 7, 11]
+    assert SumOfMultiples.to(10000, multiples) == 39_614_537
+  end
+end

elixir/sum-of-multiples/test/test_helper.exs

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