From ecb7df09a8d25245bd032693aafcb126bc602a94 Mon Sep 17 00:00:00 2001
From: Jonathan Chan <jonathanhwchan@gmail.com>
Date: Mon, 21 Dec 2020 22:43:07 -0800
Subject: [PATCH] Day 22: Cleanup

---
 src/22.rkt | 77 ++++++++++++++++++++++++------------------------------
 1 file changed, 34 insertions(+), 43 deletions(-)

diff --git a/src/22.rkt b/src/22.rkt
index 112c01a..aa9b3e8 100644
--- a/src/22.rkt
+++ b/src/22.rkt
@@ -24,48 +24,39 @@
            (combat (rest player1)
                    (append (rest player2) (list p2 p1)))))]))
 
-(define memo (make-hash '()))
-
-(define (recursive-combat player1 player2 game)
-  (if (hash-has-key? memo (list player1 player2))
-      (hash-ref memo (list player1 player2))
-      #;(printf "~a " game)
-      (let loop ([player1* player1]
-                 [player2* player2]
-                 [seen (set)])
-        (cond
-          [(empty? player1*)
-           (hash-set! memo (list player1 player2) (list #f player2*))
-           (list #f player2*)]
-          [(empty? player2*)
-           (hash-set! memo (list player1 player2) (list #t player1*))
-           (list #t player1*)]
-          [(set-member? seen (list player1* player2*))
-           (hash-set! memo (list player1 player2) (list #t player1*))
-           (list #t player1*)]
-          [else
-           (let ([p1 (first player1*)]
-                 [p2 (first player2*)]
-                 [seen (set-add seen (list player1* player2*))])
-             (cond
-               [(and (<= p1 (sub1 (length player1*)))
-                     (<= p2 (sub1 (length player2*))))
-                (match-let ([(list p1-won? deck) (recursive-combat (take (rest player1*) p1) (take (rest player2*) p2) (add1 game))])
-                  (if p1-won?
-                      (loop (append (rest player1*) (list p1 p2))
-                            (rest player2*)
-                            seen)
-                      (loop (rest player1*)
-                            (append (rest player2*) (list p2 p1))
-                            seen)))]
-               [(> p1 p2)
-                (loop (append (rest player1*) (list p1 p2))
-                      (rest player2*)
-                      seen)]
-               [(< p1 p2)
-                (loop (rest player1*)
-                      (append (rest player2*) (list p2 p1))
-                      seen)]))]))))
+(define (recursive-combat player1 player2)
+  (let loop ([player1 player1]
+             [player2 player2]
+             [seen (set)])
+    (cond
+      [(empty? player1) (list #f player2)]
+      [(empty? player2) (list #t player1)]
+      [(set-member? seen (list player1 player2)) (list #t player1)]
+      [else
+       (let ([p1 (first player1)]
+             [p2 (first player2)]
+             [seen (set-add seen (list player1 player2))])
+         (cond
+           [(and (<= p1 (sub1 (length player1)))
+                 (<= p2 (sub1 (length player2))))
+            (match-define (list p1-won? deck)
+              (recursive-combat (take (rest player1) p1)
+                                (take (rest player2) p2)))
+            (if p1-won?
+                (loop (append (rest player1) (list p1 p2))
+                      (rest player2)
+                      seen)
+                (loop (rest player1)
+                      (append (rest player2) (list p2 p1))
+                      seen))]
+           [(> p1 p2)
+            (loop (append (rest player1) (list p1 p2))
+                  (rest player2)
+                  seen)]
+           [(< p1 p2)
+            (loop (rest player1)
+                  (append (rest player2) (list p2 p1))
+                  seen)]))])))
 
 (define part1
   (let ([deck (combat player1 player2)])
@@ -74,7 +65,7 @@
       (* card score))))
 
 (define part2
-  (match-let ([(list _ deck) (recursive-combat player1 player2 1)])
+  (match-let ([(list _ deck) (recursive-combat player1 player2)])
     (for/sum ([card deck]
               [score (reverse (range 1 (add1 (length deck))))])
       (* card score))))