Add Poker exercise (#559)

config.json

@@ -941,6 +941,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "poker",
+        "name": "Poker",
+        "uuid": "5eee3bb6-bcb8-4056-a854-805ecc4dd903",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "connect",
         "name": "Connect",

exercises/practice/poker/.docs/instructions.md

@@ -0,0 +1,7 @@
+# Instructions
+
+Pick the best hand(s) from a list of poker hands.
+
+See [wikipedia][poker-hands] for an overview of poker hands.
+
+[poker-hands]: https://en.wikipedia.org/wiki/List_of_poker_hands

exercises/practice/poker/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": ["ryanplusplus"],
+  "files": {
+    "solution": [
+      "src/poker.cr"
+    ],
+    "test": [
+      "spec/poker_spec.cr"
+    ],
+    "example": [
+      ".meta/src/example.cr"
+    ]
+  },
+  "blurb": "Pick the best hand(s) from a list of poker hands.",
+  "source": "Inspired by the training course from Udacity.",
+  "source_url": "https://www.udacity.com/course/design-of-computer-programs--cs212"
+}

exercises/practice/poker/.meta/src/example.cr

@@ -0,0 +1,198 @@
+module Poker
+  def self.best_hands(hands)
+    hands = hands.map { |hand| Hand.new(hand) }
+    max_score = hands.map(&.score).max
+    hands.select { |hand| hand.score == max_score }.map(&.to_s)
+  end
+end
+
+class Poker::Hand
+  @cards : Array(Card)
+  @s : String
+
+  def initialize(@s)
+    @cards = @s.split.map { |card| Card.new(card) }
+  end
+
+  def to_s
+    @s
+  end
+
+  def score
+    straight_flush ||
+      straight_flush_ace_low ||
+      four_of_a_kind ||
+      full_house ||
+      flush ||
+      straight ||
+      straight_ace_low ||
+      three_of_a_kind ||
+      two_pair ||
+      pair ||
+      high_card
+  end
+
+  private def partitioned_by_rank
+    @cards.group_by { |card| card.rank }.values
+  end
+
+  private def partitioned_by_suit
+    @cards.group_by { |card| card.suit }.values
+  end
+
+  private def sorted_by_rank(cards = @cards)
+    cards.sort_by { |card| card.rank }.reverse
+  end
+
+  private def sorted_by_rank_ace_low
+    @cards.sort_by { |card| card.rank_ace_low }.reverse
+  end
+
+  private def base_score(type)
+    {
+      :high_card       => 1,
+      :pair            => 2,
+      :two_pair        => 3,
+      :three_of_a_kind => 4,
+      :straight        => 5,
+      :flush           => 6,
+      :full_house      => 7,
+      :four_of_a_kind  => 8,
+      :straight_flush  => 9,
+    }[type]
+  end
+
+  private def fractional_score(cards, rank_type = :rank)
+    ranks = rank_type == :rank_ace_low ? cards.map(&.rank_ace_low) : cards.map(&.rank)
+    ranks += [0, 0, 0, 0, 0]
+    [
+      ranks[0] * 0.01,
+      ranks[1] * 0.00_01,
+      ranks[2] * 0.00_00_01,
+      ranks[3] * 0.00_00_00_01,
+      ranks[4] * 0.00_00_00_00_01,
+    ].sum
+  end
+
+  private def high_card
+    base_score(:high_card) + fractional_score(sorted_by_rank)
+  end
+
+  private def pair
+    pairs = partitioned_by_rank.select { |p| p.size == 2 }
+
+    if pairs.size == 1
+      everything_else = partitioned_by_rank.select { |p| p.size == 1 }.flatten
+      base_score(:pair) + fractional_score([pairs.first.first, *sorted_by_rank(everything_else)])
+    end
+  end
+
+  private def two_pair
+    pairs = partitioned_by_rank.select { |p| p.size == 2 }
+
+    if pairs.size == 2
+      everything_else = partitioned_by_rank.select { |p| p.size == 1 }.flatten
+      pair_ranks = pairs.flatten.map(&.rank)
+      base_score(:two_pair) + fractional_score([
+        pairs.flatten.max_by { |c| c.rank },
+        pairs.flatten.min_by { |c| c.rank },
+        *sorted_by_rank(everything_else),
+      ])
+    end
+  end
+
+  private def three_of_a_kind
+    triples = partitioned_by_rank.select { |p| p.size == 3 }
+
+    if triples.size == 1
+      everything_else = partitioned_by_rank.select { |p| p.size == 1 }.flatten
+      base_score(:three_of_a_kind) + fractional_score([triples.first.first, *sorted_by_rank(everything_else)])
+    end
+  end
+
+  private def straight
+    cards = sorted_by_rank
+
+    if cards.each_cons(2).all? { |pair| pair[1].rank + 1 == pair[0].rank }
+      return base_score(:straight) + fractional_score([cards.last])
+    end
+  end
+
+  private def straight_ace_low
+    cards = sorted_by_rank_ace_low
+
+    if cards.each_cons(2).all? { |pair| pair[1].rank_ace_low + 1 == pair[0].rank_ace_low }
+      base_score(:straight) + fractional_score([cards.last], :rank_ace_low)
+    end
+  end
+
+  private def flush
+    cards = partitioned_by_suit
+
+    if cards.size == 1
+      base_score(:flush) + fractional_score([*sorted_by_rank(cards.first)])
+    end
+  end
+
+  private def full_house
+    triples = partitioned_by_rank.select { |p| p.size == 3 }
+    pairs = partitioned_by_rank.select { |p| p.size == 2 }
+
+    if pairs.size == 1 && triples.size == 1
+      base_score(:full_house) + fractional_score([triples.first.first, pairs.first.first])
+    end
+  end
+
+  private def four_of_a_kind
+    quads = partitioned_by_rank.select { |p| p.size == 4 }
+
+    if quads.size == 1
+      everything_else = partitioned_by_rank.select { |p| p.size == 1 }
+      base_score(:four_of_a_kind) + fractional_score([quads.first.first, *everything_else.flatten])
+    end
+  end
+
+  private def straight_flush
+    if straight && flush
+      base_score(:straight_flush) + fractional_score([sorted_by_rank.last])
+    end
+  end
+
+  private def straight_flush_ace_low
+    if straight_ace_low && flush
+      base_score(:straight_flush) + fractional_score([sorted_by_rank_ace_low.last], :rank_ace_low)
+    end
+  end
+end
+
+class Poker::Hand::Card
+  getter suit : Char, rank : Int32, rank_ace_low : Int32
+
+  def initialize(s)
+    @rank = parse_rank(s)
+    @rank_ace_low = parse_rank_ace_low(s)
+    @suit = parse_suit(s)
+  end
+
+  private def parse_rank(s)
+    {
+      'J' => 11,
+      'Q' => 12,
+      'K' => 13,
+      'A' => 14,
+    }[s[0]]? || s[0...-1].to_i
+  end
+
+  private def parse_rank_ace_low(s)
+    {
+      'J' => 11,
+      'Q' => 12,
+      'K' => 13,
+      'A' => 1,
+    }[s[0]]? || s[0...-1].to_i
+  end
+
+  private def parse_suit(s)
+    s[-1]
+  end
+end

exercises/practice/poker/.meta/test_template.ecr

@@ -0,0 +1,12 @@
+require "spec"
+require "../src/*"
+
+describe <%= to_capitalized(@json["exercise"].to_s) %> do
+    <% @json["cases"].as_a.each do |cases| %>
+        <%= status()%> "<%-= cases["description"] %>" do
+            hands = <%= cases["input"]["hands"].inspect.gsub("[", "[\n").gsub("\", \"", "\",\n\"") %>
+            expected = <%= cases["expected"].inspect.gsub("[", "[\n").gsub("\", \"", "\",\n\"") %>
+            <%= to_capitalized(@json["exercise"].to_s) %>.<%= cases["property"].to_s.underscore %>(hands).should eq(expected)
+        end
+    <% end %>
+end

exercises/practice/poker/.meta/tests.toml

@@ -0,0 +1,131 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[161f485e-39c2-4012-84cf-bec0c755b66c]
+description = "single hand always wins"
+
+[370ac23a-a00f-48a9-9965-6f3fb595cf45]
+description = "highest card out of all hands wins"
+
+[d94ad5a7-17df-484b-9932-c64fc26cff52]
+description = "a tie has multiple winners"
+
+[61ed83a9-cfaa-40a5-942a-51f52f0a8725]
+description = "multiple hands with the same high cards, tie compares next highest ranked, down to last card"
+
+[da01becd-f5b0-4342-b7f3-1318191d0580]
+description = "winning high card hand also has the lowest card"
+
+[f7175a89-34ff-44de-b3d7-f6fd97d1fca4]
+description = "one pair beats high card"
+
+[e114fd41-a301-4111-a9e7-5a7f72a76561]
+description = "highest pair wins"
+
+[b3acd3a7-f9fa-4647-85ab-e0a9e07d1365]
+description = "both hands have the same pair, high card wins"
+
+[935bb4dc-a622-4400-97fa-86e7d06b1f76]
+description = "two pairs beats one pair"
+
+[c8aeafe1-6e3d-4711-a6de-5161deca91fd]
+description = "both hands have two pairs, highest ranked pair wins"
+
+[88abe1ba-7ad7-40f3-847e-0a26f8e46a60]
+description = "both hands have two pairs, with the same highest ranked pair, tie goes to low pair"
+
+[15a7a315-0577-47a3-9981-d6cf8e6f387b]
+description = "both hands have two identically ranked pairs, tie goes to remaining card (kicker)"
+
+[f761e21b-2560-4774-a02a-b3e9366a51ce]
+description = "both hands have two pairs that add to the same value, win goes to highest pair"
+
+[fc6277ac-94ac-4078-8d39-9d441bc7a79e]
+description = "two pairs first ranked by largest pair"
+
+[21e9f1e6-2d72-49a1-a930-228e5e0195dc]
+description = "three of a kind beats two pair"
+
+[c2fffd1f-c287-480f-bf2d-9628e63bbcc3]
+description = "both hands have three of a kind, tie goes to highest ranked triplet"
+
+[eb856cc2-481c-4b0d-9835-4d75d07a5d9d]
+description = "with multiple decks, two players can have same three of a kind, ties go to highest remaining cards"
+include = false
+
+[26a4a7d4-34a2-4f18-90b4-4a8dd35d2bb1]
+description = "with multiple decks, two players can have same three of a kind, ties go to highest remaining cards"
+reimplements = "eb856cc2-481c-4b0d-9835-4d75d07a5d9d"
+
+[a858c5d9-2f28-48e7-9980-b7fa04060a60]
+description = "a straight beats three of a kind"
+
+[73c9c756-e63e-4b01-a88d-0d4491a7a0e3]
+description = "aces can end a straight (10 J Q K A)"
+
+[76856b0d-35cd-49ce-a492-fe5db53abc02]
+description = "aces can start a straight (A 2 3 4 5)"
+
+[e214b7df-dcba-45d3-a2e5-342d8c46c286]
+description = "aces cannot be in the middle of a straight (Q K A 2 3)"
+
+[6980c612-bbff-4914-b17a-b044e4e69ea1]
+description = "both hands with a straight, tie goes to highest ranked card"
+
+[5135675c-c2fc-4e21-9ba3-af77a32e9ba4]
+description = "even though an ace is usually high, a 5-high straight is the lowest-scoring straight"
+
+[c601b5e6-e1df-4ade-b444-b60ce13b2571]
+description = "flush beats a straight"
+
+[4d90261d-251c-49bd-a468-896bf10133de]
+description = "both hands have a flush, tie goes to high card, down to the last one if necessary"
+include = false
+
+[e04137c5-c19a-4dfc-97a1-9dfe9baaa2ff]
+description = "both hands have a flush, tie goes to high card, down to the last one if necessary"
+reimplements = "4d90261d-251c-49bd-a468-896bf10133de"
+
+[3a19361d-8974-455c-82e5-f7152f5dba7c]
+description = "full house beats a flush"
+
+[eb73d0e6-b66c-4f0f-b8ba-bf96bc0a67f0]
+description = "both hands have a full house, tie goes to highest-ranked triplet"
+
+[34b51168-1e43-4c0d-9b32-e356159b4d5d]
+description = "with multiple decks, both hands have a full house with the same triplet, tie goes to the pair"
+
+[d61e9e99-883b-4f99-b021-18f0ae50c5f4]
+description = "four of a kind beats a full house"
+
+[2e1c8c63-e0cb-4214-a01b-91954490d2fe]
+description = "both hands have four of a kind, tie goes to high quad"
+
+[892ca75d-5474-495d-9f64-a6ce2dcdb7e1]
+description = "with multiple decks, both hands with identical four of a kind, tie determined by kicker"
+
+[923bd910-dc7b-4f7d-a330-8b42ec10a3ac]
+description = "straight flush beats four of a kind"
+
+[d9629e22-c943-460b-a951-2134d1b43346]
+description = "aces can end a straight flush (10 J Q K A)"
+
+[05d5ede9-64a5-4678-b8ae-cf4c595dc824]
+description = "aces can start a straight flush (A 2 3 4 5)"
+
+[ad655466-6d04-49e8-a50c-0043c3ac18ff]
+description = "aces cannot be in the middle of a straight flush (Q K A 2 3)"
+
+[d0927f70-5aec-43db-aed8-1cbd1b6ee9ad]
+description = "both hands have a straight flush, tie goes to highest-ranked card"
+
+[be620e09-0397-497b-ac37-d1d7a4464cfc]
+description = "even though an ace is usually high, a 5-high straight flush is the lowest-scoring straight flush"