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shockbob's solution

to Poker in the Clojure Track

Published at Oct 16 2018 · 0 comments
Instructions
Test suite
Solution

Pick the best hand(s) from a list of poker hands.

See wikipedia for an overview of poker hands.

Source

Inspired by the training course from Udacity. https://www.udacity.com/course/viewer#!/c-cs212/

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

poker_test.clj

(ns poker-test
(:require [clojure.test :refer [deftest is]]
[poker :refer [best-hands]]))

(defn f [xs ys] (= (sort (best-hands xs)) (sort ys)))

(deftest single-hand-always-wins
(is (f ["4S 5S 7H 8D JC"] ["4S 5S 7H 8D JC"])))

(deftest highest-card-out-of-all-hands-wins
(is (f ["4D 5S 6S 8D 3C"
"2S 4C 7S 9H 10H"
"3S 4S 5D 6H JH"]
["3S 4S 5D 6H JH"])))

(deftest a-tie-has-multiple-winners
(is (f ["4D 5S 6S 8D 3C"
"2S 4C 7S 9H 10H"
"3S 4S 5D 6H JH"
"3H 4H 5C 6C JD"]
["3S 4S 5D 6H JH"
"3H 4H 5C 6C JD"])))

(deftest multiple-hands-with-the-same-high-cards-tie-compares-next-highest-ranked-down-to-last-card
(is (f ["3S 5H 6S 8D 7H"
"2S 5D 6D 8C 7S"]
["3S 5H 6S 8D 7H"])))

(deftest one-pair-beats-high-card
(is (f ["4S 5H 6C 8D KH"
"2S 4H 6S 4D JH"]
["2S 4H 6S 4D JH"])))

(deftest highest-pair-wins
(is (f ["4S 2H 6S 2D JH"
"2S 4H 6C 4D JD"]
["2S 4H 6C 4D JD"])))

(deftest two-pairs-beats-one-pair
(is (f ["2S 8H 6S 8D JH"
"4S 5H 4C 8C 5C"]
["4S 5H 4C 8C 5C"])))

(deftest both-hands-have-two-pairs-highest-ranked-pair-wins
(is (f ["2S 8H 2D 8D 3H"
"4S 5H 4C 8S 5D"]
["2S 8H 2D 8D 3H"])))

(deftest both-hands-have-two-pairs-with-the-same-highest-ranked-pair-tie-goes-to-low-pair
(is (f ["2S QS 2C QD JH"
"JD QH JS 8D QC"]
["JD QH JS 8D QC"])))

(deftest both-hands-have-two-identically-ranked-pairs-tie-goes-to-remaining-card-kicker
(is (f ["JD QH JS 8D QC"
"JS QS JC 2D QD"]
["JD QH JS 8D QC"])))

(deftest three-of-a-kind-beats-two-pair
(is (f ["2S 8H 2H 8D JH"
"4S 5H 4C 8S 4H"]
["4S 5H 4C 8S 4H"])))

(deftest both-hands-have-three-of-a-kind-tie-goes-to-highest-ranked-triplet
(is (f ["2S 2H 2C 8D JH"

(deftest with-multiple-decks-two-players-can-have-same-three-of-a-kind-ties-go-to-highest-remaining-cards
(is (f ["4S AH AS 7C AD"

(deftest a-straight-beats-three-of-a-kind
(is (f ["4S 5H 4C 8D 4H"
"3S 4D 2S 6D 5C"]
["3S 4D 2S 6D 5C"])))

(deftest aces-can-end-a-straight-10-J-Q-K-A
(is (f ["4S 5H 4C 8D 4H"
"10D JH QS KD AC"]
["10D JH QS KD AC"])))

(deftest aces-can-start-a-straight-A-2-3-4-5
(is (f ["4S 5H 4C 8D 4H"
"4D AH 3S 2D 5C"]
["4D AH 3S 2D 5C"])))

(deftest both-hands-with-a-straight-tie-goes-to-highest-ranked-card
(is (f ["4S 6C 7S 8D 5H"
"5S 7H 8S 9D 6H"]
["5S 7H 8S 9D 6H"])))

(deftest even-though-an-ace-is-usually-high-a-5-high-straight-is-the-lowest-scoring-straight
(is (f ["2H 3C 4D 5D 6H"
"4S AH 3S 2D 5H"]
["2H 3C 4D 5D 6H"])))

(deftest flush-beats-a-straight
(is (f ["4C 6H 7D 8D 5H"
"2S 4S 5S 6S 7S"]
["2S 4S 5S 6S 7S"])))

(deftest both-hands-have-a-flush-tie-goes-to-high-card-down-to-the-last-one-if-necessary
(is (f ["4H 7H 8H 9H 6H"
"2S 4S 5S 6S 7S"]
["4H 7H 8H 9H 6H"])))

(deftest full-house-beats-a-flush
(is (f ["3H 6H 7H 8H 5H"
"4S 5H 4C 5D 4H"]
["4S 5H 4C 5D 4H"])))

(deftest both-hands-have-a-full-house-tie-goes-to-highest-ranked-triplet
(is (f ["4H 4S 4D 9S 9D"
"5H 5S 5D 8S 8D"]
["5H 5S 5D 8S 8D"])))

(deftest with-multiple-decks-both-hands-have-a-full-house-with-the-same-triplet-tie-goes-to-the-pair
(is (f ["5H 5S 5D 9S 9D"
"5H 5S 5D 8S 8D"]
["5H 5S 5D 9S 9D"])))

(deftest four-of-a-kind-beats-a-full-house
(is (f ["4S 5H 4D 5D 4H"
"3S 3H 2S 3D 3C"]
["3S 3H 2S 3D 3C"])))

(is (f ["2S 2H 2C 8D 2D"
"4S 5H 5S 5D 5C"]
["4S 5H 5S 5D 5C"])))

(deftest with-multiple-decks-both-hands-with-identical-four-of-a-kind-tie-determined-by-kicker
(is (f ["3S 3H 2S 3D 3C"
"3S 3H 4S 3D 3C"]
["3S 3H 4S 3D 3C"])))

(deftest straight-flush-beats-four-of-a-kind
(is (f ["4S 5H 5S 5D 5C"
"7S 8S 9S 6S 10S"]
["7S 8S 9S 6S 10S"])))

(deftest both-hands-have-straight-flush-tie-goes-to-highest-ranked-card
(is (f ["4H 6H 7H 8H 5H"
"5S 7S 8S 9S 6S"]
["5S 7S 8S 9S 6S"])))
(ns poker)

(def rank-map {"2" 2 "3" 3 "4" 4 "5" 5 "6" 6 "7" 7
"8" 8 "9" 9 "10" 10 "J" 11 "Q" 12 "K" 13 "A" 14})

(defn rank [st] (rank-map (.substring st 0 (dec (count st)))))
(defn suit [st] (.substring st (dec (count st))))

(defn make-rank-thing [cards]
(sort-by val (frequencies (map rank cards))))

(def straight-array [14 2 3 4 5 6 7 8 9 10 11 12 13 14])

(def straights (map set (partition 5 1 straight-array)))

(defn straight [cards]
(let [ranks (set (map rank cards))]
(some (partial = ranks) straights)))

(defn rank15 ([coll] (rank15 coll 0))
([coll sum]
(if (empty? coll)
sum
(let [sum (+ (first coll) (* sum 15)) ]
(rank15 (rest coll) sum)))))

(defn high-card [hand]
(apply max (map rank hand)))

(defn high-card-1 [hand]
(->> hand
(map rank)
(frequencies)
(sort-by (juxt last first))
(reverse)
(map first)
(rank15)))

(defn high-card-straight [cards]
(let [ranks (set (map rank cards))
match-count (count (filter #{14 2} ranks))
low-ace (= 2 match-count)
ranks (if low-ace (remove #{14} ranks) ranks) ]
(apply max ranks)))

(defn flushh [cards]
(= 1 (count (distinct (map suit cards)))))

(defn straight-flush [cards]
(and (flushh cards) (straight cards)))

(defn getmatcher [pattern]
(fn [cards] (let
[rank-thing (make-rank-thing cards)
sorted-ranks (map last rank-thing)]
(= sorted-ranks pattern))))

(defn hand-rank [[type score matcher addon]]

(def hand-type
[[:straight-flushh 100000 straight-flush high-card-straight]
[:four-of-a-kind 90000 (getmatcher [1 4]) high-card-1]
[:full-house 80000 (getmatcher [2 3]) high-card-1]
[:flush 70000 flushh high-card]
[:straight 60000 straight high-card-straight]
[:three-of-a-kind 50000 (getmatcher [1 1 3]) high-card-1]
[:two-pair 40000 (getmatcher [1 2 2]) high-card-1]
[:pair 30000 (getmatcher [1 1 1 2]) high-card-1]
[:high-card 20000 (getmatcher [1 1 1 1 1]) high-card-1]])

(def hand-types (map hand-rank hand-type))

(defn find-rank [hand]
(let [cards (vec (.split hand " "))
filt (filter (fn [ht] ((ht :matcher) cards)) hand-types)
htx (first filt)
{:score (htx :score) :extra extra-score :hand hand}))

(defn best-hands [hands]
(let [hand-scores (map (fn [hand] (find-rank hand) ) hands)
mx (apply max (map :score hand-scores))
besties (filter (fn [hand-score] (= mx (hand-score :score))) hand-scores)
mx (apply max (map :extra besties))
bestbest (filter (fn [hand-score] (= mx (hand-score :extra))) besties)
besthands (map :hand bestbest) ]
besthands))