catch up

data/day13.txt

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+
+fold along x=655
+fold along y=447
+fold along x=327
+fold along y=223
+fold along x=163
+fold along y=111
+fold along x=81
+fold along y=55
+fold along x=40
+fold along y=27
+fold along y=13
+fold along y=6

data/day14.test.txt

@@ -0,0 +1,18 @@
+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C

data/day14.txt

@@ -0,0 +1,102 @@
+OFSVVSFOCBNONHKFHNPK
+
+HN -> C
+VB -> K
+PF -> C
+BO -> F
+PB -> F
+OH -> H
+OB -> N
+PN -> O
+KO -> V
+CK -> V
+FP -> H
+PC -> V
+PP -> N
+FN -> N
+CC -> F
+FC -> N
+BP -> N
+SH -> F
+NS -> V
+KK -> B
+HS -> C
+NV -> N
+FO -> B
+VO -> S
+KN -> F
+SC -> V
+NB -> H
+CH -> B
+SF -> V
+NP -> V
+FB -> P
+CV -> B
+PO -> P
+SV -> P
+OO -> V
+PS -> C
+CO -> N
+SP -> B
+KP -> H
+KH -> S
+KS -> S
+NH -> K
+SS -> P
+PV -> P
+KV -> V
+ON -> N
+BS -> C
+HP -> K
+SB -> P
+VC -> B
+HB -> N
+FS -> V
+VP -> K
+BB -> N
+FK -> S
+CS -> P
+SO -> F
+HF -> F
+VV -> C
+BC -> S
+SN -> K
+KB -> H
+BN -> H
+HO -> S
+KC -> F
+CP -> S
+HC -> S
+OS -> K
+NK -> N
+BF -> S
+VN -> B
+SK -> K
+HV -> B
+KF -> H
+FV -> B
+VF -> H
+BH -> S
+NN -> O
+HH -> K
+CN -> H
+PH -> V
+NF -> S
+OV -> P
+OC -> V
+OK -> H
+OF -> H
+HK -> N
+FH -> P
+BK -> N
+VS -> H
+NO -> V
+VK -> K
+CF -> N
+CB -> N
+NC -> K
+PK -> B
+VH -> F
+FF -> C
+BV -> P
+OP -> K

data/day15.txt

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day12.rkt

@@ -1,75 +1,37 @@
 #lang racket
 (require "lib/common.rkt"
+         fancy-app
          graph)
 
-(define (string-upcase? str)
-  (for/and ([ch (in-string str)])
+(define (big-cave? vtx)
+  (for/and ([ch (in-string vtx)])
     (char-upper-case? ch)))
 
-(define (day12a lines)
-  (define G
-    (undirected-graph
-     (for/list ([str (in-list lines)])
-       (string-split str "-"))))
-  (define-vertex-property G size)
-  (for ([vertex (in-vertices G)])
-    (size-set!
-     vertex
-     (cond [(string=? vertex "start") 'start]
-           [(string=? vertex "end") 'end]
-           [(string-upcase? vertex) 'big]
-           [else 'small])))
+(define (parse lines)
+  (undirected-graph (map (string-split _ "-") lines)))
 
-  (define (run-dfs vertex [seen (set "start")])
-    (cond [(string=? vertex "end") 1]
-          [else
-           (for/sum ([adj (in-neighbors G vertex)]
-                     #:when (not (set-member? seen adj)))
-             (run-dfs adj
-                      (if (equal? (size adj) 'small)
-                          (set-add seen adj)
-                          seen)))]))
+(define (walk G did-twice? [vertex "start"] [seen (set "start")])
+  (for*/sum ([adj (in-neighbors G vertex)]
+             [big? (in-value (big-cave? adj))]
+             [seen? (in-value (set-member? seen adj))]
+             #:when (or big? (not seen?) (not did-twice?))
+             #:unless (equal? adj "start"))
+    (cond [(string=? adj "end") 1]
+          [else (walk G
+                      (or did-twice? (and (not big?) seen?))
+                      adj
+                      (set-add seen adj))])))
 
-  (run-dfs "start"))
+(define (day12a G)
+  (walk G #t))
 
-(define (day12b lines)
-  (define G
-    (undirected-graph
-     (for/list ([str (in-list lines)])
-       (string-split str "-"))))
-  (define-vertex-property G size)
-  (for ([vertex (in-vertices G)])
-    (size-set!
-     vertex
-     (cond [(string=? vertex "start") 'start]
-           [(string=? vertex "end") 'end]
-           [(string-upcase? vertex) 'big]
-           [else 'small])))
-
-  (define (run-dfs vertex [seen (set "start")] [special #f])
-    (cond [(string=? vertex "end") 1]
-          [else
-           (for/sum ([adj (in-neighbors G vertex)]
-                     #:when (not (set-member? seen adj)))
-             (define reg
-               (run-dfs adj
-                        (if (equal? (size adj) 'small)
-                            (set-add seen adj)
-                            seen)
-                        special))
-             (define (spc)
-               (run-dfs adj seen #t))
-             (if (and (not special)
-                      (equal? (size adj) 'small))
-                 (+ (spc) reg)
-                 reg))]))
-
-  (run-dfs "start"))
+(define (day12b G)
+  (walk G #f))
 
 (module+ main
   (call-with-input-file "data/day12.txt"
     (λ (prt)
-      (define lines (port->lines prt))
+      (define lines (parse (port->lines prt)))
       (answer 12 1 (day12a lines))
       (answer 12 2 (day12b lines)))))
 
@@ -86,5 +48,5 @@ A-end
 b-end
 EOD
     )
-  (check-equal? (day12a (string-split lines)) 10)
-  (check-equal? (day12b (string-split lines)) 36))
+  (check-equal? (day12a (parse (string-split lines))) 10)
+  (check-equal? (day12b (parse (string-split lines))) 36))

day13.rkt

@@ -0,0 +1,61 @@
+#lang racket
+(require "lib/common.rkt")
+
+(struct posn (x y) #:transparent)
+(struct fold (axis n) #:transparent)
+
+(define (parse input)
+  (match-define `(,paper ,instrs) (string-split input "\n\n"))
+  (values (for/set ([p (in-list (string-split paper))])
+            (match-define (pregexp #px"([0-9]+),([0-9]+)"
+                                   (list _
+                                         (app string->number x)
+                                         (app string->number y)))
+              p)
+            (posn x y))
+          (for/list ([instr (in-list (string-split instrs "\n"))])
+            (match-define (pregexp #px"fold along (x|y)=([0-9]+)"
+                                   (list _
+                                         (app string->symbol axis)
+                                         (app string->number n)))
+              instr)
+            (fold axis n))))
+
+(define (fold-along paper instr)
+  (for/set ([p (in-set paper)])
+    (match-define (posn x y) p)
+    (match instr
+      [(fold 'x n) #:when (> x n) (posn (- (* 2 n) x) y)]
+      [(fold 'y n) #:when (> y n) (posn x (- (* 2 n) y))]
+      [_ p])))
+
+(define (day13a paper instrs)
+  (set-count (fold-along paper (first instrs))))
+
+(define (max-on-axis paper axis)
+  (for/max ([pt (in-set paper)])
+    (match axis
+      ['x (posn-x pt)]
+      ['y (posn-y pt)])))
+
+(define (print-paper paper)
+  (for ([y (in-inclusive-range 0 (max-on-axis paper 'y))])
+    (displayln
+     (apply string
+            (for/list ([x (in-inclusive-range 0 (max-on-axis paper 'x))])
+              (cond [(set-member? paper (posn x y)) #\█]
+                    [else #\space]))))))
+
+(define (day13b paper instrs)
+  (print-paper
+   (for/fold ([cur-paper paper])
+             ([instr (in-list instrs)])
+     (fold-along cur-paper instr))))
+
+(module+ main
+  (call-with-input-file "data/day13.txt"
+    (λ (prt)
+      (define-values (paper instrs) (parse (port->string prt)))
+      (answer 13 1 (day13a paper instrs))
+      (displayln "answer 13.2:")
+      (day13b paper instrs))))

day14.rkt

@@ -0,0 +1,62 @@
+#lang racket
+(require "lib/common.rkt"
+         fancy-app
+         threading)
+
+(define (parse input)
+  (match-define `(,poly-str ,rules) (string-split input "\n\n"))
+  (values (for/fold ([hsh (hash)])
+                    ([tortoise (in-string poly-str)]
+                     [hare (in-list (rest (string->list poly-str)))])
+            (hash-update hsh (cons (string tortoise) (string hare)) add1 0))
+          (for/hash ([rule (in-list (string-split rules "\n"))])
+            (match-define (pregexp "(.)(.) -> (.)" (list _ ch1 ch2 ch3)) rule)
+            (values (cons ch1 ch2) ch3))))
+
+(define (step poly rules)
+  (for/fold ([hsh (hash)])
+            ([(pair num) (in-hash poly)])
+    (match-define (cons l r) pair)
+    (define i (hash-ref rules pair))
+    (~> hsh
+        (hash-update (cons l i) (+ _ num) 0)
+        (hash-update (cons i r) (+ _ num) 0))))
+
+(define (score poly)
+  (define freqs
+    (for/fold ([hsh (hash)])
+              ([(pair num) (in-hash poly)])
+      (match-define (cons l r) pair)
+      (~> hsh
+          (hash-update l (+ _ num) 0)
+          (hash-update r (+ _ num) 0))))
+  (floor
+   (- (/ (apply max (hash-values freqs)) 2)
+      (/ (apply min (hash-values freqs)) 2))))
+
+(define (day14a poly rules)
+  (score
+   (for/fold ([cur-poly poly])
+             ([_ (in-range 10)])
+     (step cur-poly rules))))
+
+(define (day14b poly rules)
+  (score
+   (for/fold ([cur-poly poly])
+             ([_ (in-range 40)])
+     (step cur-poly rules))))
+
+(module+ main
+  (call-with-input-file "data/day14.txt"
+    (λ (prt)
+      (define-values (poly rules) (parse (port->string prt)))
+      #;(answer 14 1 (day14a poly rules))
+      (answer 14 2 (day14b poly rules)))))
+
+(module+ test
+  (require rackunit)
+
+  (call-with-input-file "data/day14.test.txt"
+    (λ (prt)
+      (define-values (poly rules) (parse (port->string prt)))
+      (check-equal? (day14a poly rules) 1588))))

day15.rkt

@@ -0,0 +1,115 @@
+#lang racket
+(require "lib/common.rkt"
+         fancy-app
+         graph
+         threading)
+
+(struct posn (x y) #:transparent)
+
+(define (posn+ p1 p2)
+  (posn (+ (posn-x p1) (posn-x p2))
+        (+ (posn-y p1) (posn-y p2))))
+
+(define (1norm x y)
+  (+ (abs x) (abs y)))
+
+(define ((repeat fn n) val)
+  (for/fold ([acc val])
+            ([_ (in-range n)])
+    (fn acc)))
+
+(define (explode str)
+  (map string (string->list str)))
+
+(define (parse lines)
+  (~>> lines
+       (map explode)
+       (map (λ~>> (map string->number)
+                  (apply vector)))
+       (apply vector)))
+
+(define (board-dim board)
+  (cons (vector-length (vector-ref board 0))
+        (vector-length board)))
+(define (board-ref board x y)
+  (vector-ref (vector-ref board y) x))
+
+(define (adjacents board p)
+  (match-define (cons m n) (board-dim board))
+
+  (define (valid? p)
+    (match-define (posn x y) p)
+    (not (or (< x 0) (< y 0) (>= x m) (>= y n))))
+
+  (for/list ([path (in-list (list (posn 0 1) (posn 1 0) (posn 0 -1) (posn -1 0)))]
+             #:when (valid? (posn+ path p)))
+    (posn+ path p)))
+
+(define (generate-graph board)
+  (match-define (cons m n) (board-dim board))
+  (define edges
+    (for*/list ([i (in-range 0 m)]
+                [j (in-range 0 n)]
+                [adj (in-list (adjacents board (posn i j)))])
+      (list (board-ref board (posn-x adj) (posn-y adj))
+            (posn i j) adj)))
+  (weighted-graph/directed edges))
+
+(define (day15a board)
+  (match-define (cons m n) (board-dim board))
+  (define G (generate-graph board))
+  (define-values (distances _) (dijkstra G (posn 0 0)))
+
+  (hash-ref distances (posn (sub1 m) (sub1 n))))
+
+(define (tesselate starting-board)
+  (match-define (cons m n) (board-dim starting-board))
+
+  (define (increment board)
+    ;; annoyingly not modulo
+    (vector-map (vector-map (λ (x) (if (= (add1 x) 10) 1 (add1 x))) _) board))
+
+  (define boards
+    (for*/vector ([i (in-range 5)]
+                  [j (in-range 5)])
+      ((repeat increment (1norm i j)) starting-board)))
+
+  (define (bboard-ref vec i j)
+    (~> vec
+        (vector-ref (+ (floor (/ j n)) (* 5 (floor (/ i m)))))
+        (board-ref (modulo i m) (modulo j n))))
+
+  (for/vector ([j (in-range (* 5 n))])
+    (for/vector ([i (in-range (* 5 m))])
+      (bboard-ref boards i j))))
+
+(define (day15b board)
+  (day15a (tesselate board)))
+
+(module+ main
+  (call-with-input-file "data/day15.txt"
+    (λ (prt)
+      (define board (parse (port->lines prt)))
+      (answer 15 1 (time (day15a board)))
+      (answer 15 2 (time (day15b board))))))
+
+(module+ test
+  (require rackunit)
+
+  (define test-input #<<EOD
+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581
+EOD
+    )
+
+  (define board (parse (string-split test-input)))
+  (check-equal? (day15a board) 40)
+  (check-equal? (day15b board) 315))