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# ukolka's solution

## to Poker in the Clojure Track

Published at Feb 04 2021 · 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 ranks ["2" "3" "4" "5" "6" "7" "8" "9" "10" "J" "Q" "K" "A"])
(def suits [\H \S \D \C])

(defn card [s]
(let [rank (apply str (butlast s))
suit (last s)
weight (inc (.indexOf ranks rank))]
{:rank rank
:suit suit
:weight weight
:alt-weight (if (= rank "A")
0
weight)}))

(defn normalize-hand [h]
(->> (clojure.string/split h #" ")
(map card)))

(defn group-sizes [h attr]
(->> h
(group-by attr)
(map #(count (second %)))))

(defn largest-group [h attr]
(apply max (group-sizes h attr)))

(defn largest-weight-diff [h w]
(->> h
(sort-by w)
reverse
(map w)
(partition 2 1)
(map (partial reduce -))
(apply max)))

(defn flush? [h]
(= 5 (largest-group h :suit)))

(defn straight?
([h] (straight? h :weight))
([h w]
(= 1 (largest-weight-diff h w))))

(defn straight-flush?
([h] (straight-flush? h :weight))
([h w]
(and (straight? h w)
(flush? h))))

(defn four-of-a-kind? [h]
(= 4 (largest-group h :rank)))

(defn full-house? [h]
(= #{2 3} (set (group-sizes h :rank))))

(defn three-of-a-kind? [h]
(= #{1 3} (set (group-sizes h :rank))))

(defn two-pair? [h]
(= [1 2 2] (sort (group-sizes h :rank))))

(defn one-pair? [h]
(= [1 1 1 2] (sort (group-sizes h :rank))))

(defn n-plet-weight
([h n] (n-plet-weight h n :weight))
([h n w]
(->> h
(group-by w)
(map #(vector (first %) (count (second %))))
(filter #(= n (second %)))
(map first)
sort
reverse)))

(defn hand-score [h]
(cond
(straight-flush? h) (concat [8] (n-plet-weight h 1))
(straight-flush? h :alt-weight) (concat [8] (n-plet-weight h 1 :alt-weight))
(four-of-a-kind? h) (concat [7] (n-plet-weight h 4) (n-plet-weight h 1))
(full-house? h) (concat [6] (n-plet-weight h 3) (n-plet-weight h 2))
(flush? h) (concat [5] (n-plet-weight h 1))
(straight? h) (concat [4] (n-plet-weight h 1))
(straight? h :alt-weight) (concat [4] (n-plet-weight h 1 :alt-weight))
(three-of-a-kind? h) (concat [3] (n-plet-weight h 3) (n-plet-weight h 1))
(two-pair? h) (concat [2] (n-plet-weight h 2) (n-plet-weight h 1))
(one-pair? h) (concat [1] (n-plet-weight h 2) (n-plet-weight h 1))
:else (concat [0] (n-plet-weight h 1))))

(defn compare-scores [s1 s2]
(let [compare-len (min (count s1) (count s2))]
(compare
(into [] (take compare-len s1))
(into [] (take compare-len s2)))))

(defn make-hand [h]
{:hand h
:score (->> h
normalize-hand
hand-score)})

(defn best-hands [hands]
(let [ordered-hands (->> hands
(map make-hand)
(sort-by :score compare-scores)
reverse)
top-hand-score (:score (first ordered-hands))]
(->> ordered-hands
(take-while #(= (:score %) top-hand-score))
(map :hand))))``````