Solve 49 - Group Anagrams (#9)

Author: terenceponce

README.md

@@ -9,5 +9,6 @@ This is a monorepo containing my solutions to LeetCode problems written in vario
 ## List of Problems/Solutions
 
 - 1 - Two Sum - [Notes](notes/0001_two_sum.md) | [Elixir](elixir/lib/solutions/0001_two_sum/two_sum.ex) | [Ruby](ruby/lib/solutions/0001_two_sum/two_sum.rb)
+- 49 - Group Anagrams - [Notes](notes/0049_group_anagrams.md) | [Elixir](elixir/lib/solutions/0049_group_anagrams/group_anagrams.ex) | [Ruby](ruby/lib/solutions/0049_group_anagrams/group_anagrams.rb)
 - 217 - Contains Duplicate - [Notes](notes/0217_contains_duplicate.md) | [Elixir](elixir/lib/solutions/0217_contains_duplicate/contains_duplicate.ex) | [Ruby](ruby/lib/solutions/0217_contains_duplicate/contains_duplicate.rb)
 - 242 - Valid Anagram - [Notes](notes/0242_valid_anagram.md) | [Elixir](elixir/lib/solutions/0242_valid_anagram/valid_anagram.ex) | [Ruby](ruby/lib/solutions/0242_valid_anagram/valid_anagram.rb)

elixir/lib/solutions/0049_group_anagrams/group_anagrams.ex

@@ -0,0 +1,14 @@
+defmodule LeetCode.Solutions.GroupAnagrams do
+  @moduledoc false
+
+  @spec call(strs :: [String.t()]) :: [[String.t()]]
+  def call(strs) do
+    strs
+    |> Enum.group_by(fn word ->
+      word
+      |> String.graphemes()
+      |> Enum.sort()
+    end)
+    |> Map.values()
+  end
+end

elixir/test/solutions/0049_group_anagrams/group_anagrams_test.exs

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+defmodule LeetCode.Solutions.GroupAnagramsTest do
+  use ExUnit.Case, async: true
+
+  alias LeetCode.Solutions.GroupAnagrams
+
+  test "Case 1 works" do
+    input = ["eat", "tea", "tan", "ate", "nat", "bat"]
+    expected_output = [["bat"], ["eat", "tea", "ate"], ["tan", "nat"]]
+
+    assert GroupAnagrams.call(input) == expected_output
+  end
+
+  test "Case 2 works" do
+    input = [""]
+    expected_output = [[""]]
+
+    assert GroupAnagrams.call(input) == expected_output
+  end
+
+  test "Case 3 works" do
+    input = ["a"]
+    expected_output = [["a"]]
+
+    assert GroupAnagrams.call(input) == expected_output
+  end
+end

notes/0049_group_anagrams.md

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+# Group Anagrams
+
+**Link to Problem**: https://leetcode.com/problems/group-anagrams
+
+## Solutions
+
+- [Elixir](../elixir/lib/solutions/0049_group_anagrams/group_anagrams.ex)
+- [Ruby](../ruby/lib/solutions/0049_group_anagrams/group_anagrams.rb)
+
+## Description
+
+Given an array of strings `strs`, group **the anagrams** together. You can return the answer
+in **any order**.
+
+An **Anagram** is a word or phrase formed by rearranging the letters of a different word or
+phrase, typically using all the original letters exactly once.
+
+## Examples
+
+### Example 1
+
+```
+Input: strs = ["eat","tea","tan","ate","nat","bat"]
+Output: [["bat"],["nat","tan"],["ate","eat","tea"]]
+```
+
+### Example 2
+
+```
+Input: strs = [""]
+Output: [[""]]
+```
+
+### Example 3
+
+```
+Input: strs = ["a"]
+Output: [["a"]]
+```
+
+## Approach
+
+The clue for this problem is that we are asked to group the anagrams together and that we have
+to product a nested array for the output.
+
+This means that we can make use of the language's `group_by` method/function which produces a
+hash map based on the grouping criteria that we pass into it.
+
+Since this is an anagram problem, we just repeat the same solution as
+[242 - Valid Anagram](0242_valid_anagram.md) where we determine anagrams by sorting the characters
+of a given string.
+
+Once we get the hash map, we just output the values of the hash map without the keys.
+
+## Additional Thoughts
+
+This is a medium problem, but I only got here because it was part of the build up for Blind 75.
+
+The progression to get to this problem is pretty good because I at least had some idea on how to
+solve this.
+
+Of course, I didn't actually figure out the solution for this on my own and I had to look it up.

ruby/lib/solutions/0049_group_anagrams/group_anagrams.rb

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+# frozen_string_literal: true
+
+def group_anagrams(strs)
+  strs.group_by { |str| str.chars.sort }.values
+end

ruby/test/solutions/0049_group_anagrams/group_anagrams_test.rb

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+# frozen_string_literal: true
+
+require 'test_helper'
+require_relative '../../../lib/solutions/0049_group_anagrams/group_anagrams'
+
+class GroupAnagramsTest < Minitest::Test
+  def test_case_1_works
+    input = %w[eat tea tan ate nat bat]
+    expected_output = [%w[eat tea ate], %w[tan nat], %w[bat]]
+
+    assert_equal expected_output, group_anagrams(input)
+  end
+
+  def test_case_2_works
+    assert_equal [['']], group_anagrams([''])
+  end
+
+  def test_case_3_works
+    assert_equal [['a']], group_anagrams(['a'])
+  end
+end