Group Anagrams

  # 🔤 3. Group Anagrams
  # Groups words that are anagrams of each other.
  # Sorts the characters in each word and uses that sorted string as the hash key.
  # Time Complexity: O(n * k log k)
  # Where:
  # n = number of strings
  # k = average length of a string
  # Why: Each word is sorted (which takes O(k log k)), and we do that for each of the n words.
  def group_anagrams(strs)
    groups = Hash.new { |h, k| h[k] = [] }
    strs.each do |s|
      key = s.chars.sort.join
      groups[key] << s
    end
    groups.values