From e01c3a36945c41214df37d4822d341404d6802e9 Mon Sep 17 00:00:00 2001
From: Clyne Sullivan <clyne@bitgloo.com>
Date: Tue, 21 Dec 2021 13:03:03 -0500
Subject: day21: add part 2
---
day21/part2.clj | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
create mode 100644 day21/part2.clj
diff --git a/day21/part2.clj b/day21/part2.clj
new file mode 100644
index 0000000..86362f4
--- /dev/null
+++ b/day21/part2.clj
@@ -0,0 +1,30 @@
+(def rolls {3 1 4 3 5 6 6 7 7 6 8 3 9 1})
+
+(defn advance-pos [pos roll] (let [n (+ pos roll)] (if (> n 10) (- n 10) n)))
+
+(defn add-roll [state roll p1-turn]
+ (let [pos (if p1-turn :pos1 :pos2)
+ score (if p1-turn :score1 :score2)
+ new-pos (advance-pos (state pos) roll)]
+ (-> state
+ (assoc pos new-pos)
+ (update score + new-pos))))
+
+(defonce wins (atom [0 0]))
+
+(loop [turn 0 states {{:pos1 10 :score1 0 :pos2 1 :score2 0} 1}]
+ (if (empty? states)
+ (println (apply max @wins))
+ (recur
+ (if (= 0 turn) 1 0)
+ (reduce
+ #(let [kvp (first %2)]
+ (if (< ((key kvp) (if (= 0 turn) :score1 :score2)) 21)
+ (if (contains? %1 (key kvp))
+ (update %1 (key kvp) + (val kvp))
+ (conj %1 kvp))
+ (do (swap! wins update turn +' (val kvp)) %1)))
+ {}
+ (for [s states r rolls]
+ {(add-roll (first s) (key r) (= 0 turn)) (*' (second s) (val r))})))))
+
--
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