decks.rb

def full_suit?(suit)
  suit.each do |k, v|
    return false if v < 1
  end
  true
end

def solution(a)
  ranks = (2..9).map(&:to_s) + %w(T J Q K A)
  suits = %w(H D C S)
  deck = {}
  sets = {}

  ranks.each do |r|
    deck[r] = {}
    sets[r] = 0
    suits.each do |s|
      deck[r][s] = 0
    end
  end

  a.each do |c|
    r = c[0]
    s = c[1]
    deck[r][s] += 1
    if full_suit?(deck[r])
      sets[r] += 1
      deck[r].keys.each do |k|
        deck[r][k] -= 1
      end
    end
  end

  return sets.values.min
end

# ---------------------------------------------------

# Should return 0
cards = ["9C", "KS", "AC", "AH", "8D", "4C", "KD", "JC", "7D", "9D", "2H", "7C", "3C", "7S", "5C", "6H", "TH"]
puts solution(cards)

# ---------------------------------------------------

cards = []
ranks = (2..9).map(&:to_s) + %w(T J Q K A)
suits = %w(H D C S)

ranks.each do |r|
  suits.each do |s|
    cards << "#{r}#{s}"
  end
end

# Should return 1
puts solution(cards)

# ---------------------------------------------------

cards = []

2.times do
  ranks.each do |r|
    suits.each do |s|
      cards << "#{r}#{s}"
    end
  end
end

# Should return 2
puts solution(cards)