7 files changed, 177 insertions, 0 deletions
diff --git a/racket/aoc2015/day-01/day-01.rkt b/racket/aoc2015/day-01/day-01.rkt
new file mode 100644
index 0000000..efbd02a
--- /dev/null
+++ b/racket/aoc2015/day-01/day-01.rkt
@@ -0,0 +1,16 @@
+#lang racket
+(require "../../jj-aoc.rkt")
+
+;; part 1
+(for/fold ([current-floor 0]) ([l (in-input-port-chars (open-day 1 2015))] [i (in-naturals)])
+  (match l
+    [#\( (add1 current-floor)]
+    [#\) (sub1 current-floor)]))
+
+;; part 2
+(for/fold ([current-floor 0] [last-index 0] #:result (add1 last-index))
+          ([l (in-input-port-chars (open-day 1 2015))] [i (in-naturals)])
+  #:break (= current-floor -1)
+  (match l
+    [#\( (values (add1 current-floor) i)]
+    [#\) (values (sub1 current-floor) i)]))
diff --git a/racket/aoc2015/day-02/day-02.rkt b/racket/aoc2015/day-02/day-02.rkt
new file mode 100644
index 0000000..579fd00
--- /dev/null
+++ b/racket/aoc2015/day-02/day-02.rkt
@@ -0,0 +1,26 @@
+#lang racket
+(require "../../jj-aoc.rkt"
+         threading
+         racket/struct)
+
+(struct present (l w h) #:transparent)
+
+(define presents
+  (for/list ([size-string (in-lines (open-day 2 2015))])
+    (~> size-string (string-split "x") (map string->number _) (apply present _))))
+
+;; part 1
+(define (paper-area p)
+  (define main-area (~> p struct->list (combinations 2) (map (λ~> (apply * 2 _)) _) (apply + _)))
+  (define slack-area (~> p struct->list (sort <) (take 2) (apply * _)))
+  (+ main-area slack-area))
+
+(for/sum ([p (in-list presents)]) (paper-area p))
+
+;; part 2
+(define (ribbon-length p)
+  (define ribbon-around-box (~> p struct->list (sort <) (take 2) (map (λ~> (* 2)) _) (apply + _)))
+  (define ribbon-for-bow (~> p struct->list (apply * _)))
+  (+ ribbon-around-box ribbon-for-bow))
+
+(for/sum ([p (in-list presents)]) (ribbon-length p))
diff --git a/racket/aoc2015/day-03/day-03.rkt b/racket/aoc2015/day-03/day-03.rkt
new file mode 100644
index 0000000..1d44955
--- /dev/null
+++ b/racket/aoc2015/day-03/day-03.rkt
@@ -0,0 +1,28 @@
+#lang racket
+(require "../../jj-aoc.rkt"
+         threading
+         (only-in algorithms chunks-of)
+         racket/hash)
+
+(define directions
+  (for/list ([l (in-input-port-chars (open-day 3 2015))])
+    (string->symbol (string l))))
+
+(define (trace-santa dirs)
+  (define visits (make-hash))
+  (for/fold ([x 0] [y 0] #:result visits) ([dir (in-list dirs)])
+    (hash-set! visits `(,x ,y) #true)
+    (match dir
+      ['^ (values x (add1 y))]
+      ['v (values x (sub1 y))]
+      ['< (values (add1 x) y)]
+      ['> (values (sub1 x) y)])))
+
+;; part 1
+(~> directions trace-santa hash-values length)
+
+;; part 2
+(~> directions (chunks-of 2) (apply map list _) (map trace-santa _) (match-define (list real robo) _))
+
+(hash-union! real robo #:combine (λ _ #true))
+(~> real hash-values length)
diff --git a/racket/aoc2015/day-04/day-04.rkt b/racket/aoc2015/day-04/day-04.rkt
new file mode 100644
index 0000000..2c16043
--- /dev/null
+++ b/racket/aoc2015/day-04/day-04.rkt
@@ -0,0 +1,18 @@
+#lang racket
+(require "../../jj-aoc.rkt"
+         threading
+         file/md5)
+
+(define secret-key (~> (open-day 4 2015) port->string string-trim))
+
+(define (find-n-zeroes n)
+  (for/first ([i (in-naturals)]
+              #:when
+              (~>> i (~a secret-key) md5 bytes->string/utf-8 (string-prefix? _ (make-string n #\0))))
+    i))
+
+;; part 1
+(time (find-n-zeroes 5))
+
+;; part 2
+(time (find-n-zeroes 6))
diff --git a/racket/aoc2015/day-05/day-05.rkt b/racket/aoc2015/day-05/day-05.rkt
new file mode 100644
index 0000000..3449adc
--- /dev/null
+++ b/racket/aoc2015/day-05/day-05.rkt
@@ -0,0 +1,32 @@
+#lang racket
+(require "../../jj-aoc.rkt"
+         threading)
+
+(define strs (port->lines (open-day 5 2015)))
+
+;; part 1
+(define (at-least-three-vowels? str)
+  (~>> str (regexp-replace* #px"[^aeiou]" _ "") string-length (<= 3)))
+
+(define (at-least-one-pair? str)
+  (regexp-match? #px"(.)\\1{1,}" str))
+
+(define (no-forbidden-pairs? str)
+  (~>> (list "ab" "cd" "pq" "xy") (ormap (λ~>> (string-contains? str))) not))
+
+(define (nice? str)
+  (~>> (list at-least-three-vowels? at-least-one-pair? no-forbidden-pairs?) (andmap (λ (f) (f str)))))
+
+(count nice? strs)
+
+;; part 2
+(define (repeating-pair? str)
+  (regexp-match? #px"(..).*\\1" str))
+
+(define (symmetry? str)
+  (regexp-match? #px"(.).\\1" str))
+
+(define (new-nice? str)
+  (~>> (list repeating-pair? symmetry?) (andmap (λ (f) (f str)))))
+
+(count new-nice? strs)
diff --git a/racket/aoc2015/day-06/day-06.rkt b/racket/aoc2015/day-06/day-06.rkt
new file mode 100644
index 0000000..d2eed08
--- /dev/null
+++ b/racket/aoc2015/day-06/day-06.rkt
@@ -0,0 +1,49 @@
+#lang racket
+(require "../../jj-aoc.rkt"
+         threading)
+
+(struct instruction (todo x1 y1 x2 y2) #:transparent)
+
+(define (make-instruction lst)
+  (apply instruction (string->symbol (first lst)) (map string->number (rest lst))))
+
+(define instructions
+  (for/list ([l (in-lines (open-day 6 2015))])
+    (~>> l
+         (regexp-match
+          #px"(turn on|toggle|turn off) (\\d{1,3}),(\\d{1,3}) through (\\d{1,3}),(\\d{1,3})")
+         rest
+         make-instruction)))
+
+(define (vector2d-modify! vec x y f)
+  (define pos (+ x (* 1000 y)))
+  (vector-set! vec pos (f (vector-ref vec pos))))
+
+;; part 1
+(define (todo inst)
+  (match (instruction-todo inst)
+    ['|turn on| (λ _ #true)]
+    ['|turn off| (λ _ #false)]
+    ['|toggle| not]))
+
+(define (modify-light-grid inst light-grid using)
+  (for ([x (inclusive-range (instruction-x1 inst) (instruction-x2 inst))])
+    (for ([y (inclusive-range (instruction-y1 inst) (instruction-y2 inst))])
+      (vector2d-modify! light-grid x y (using inst)))))
+
+(define light-grid (make-vector (* 1000 1000) #false))
+(for ([i (in-list instructions)])
+  (modify-light-grid i light-grid todo))
+(vector-count identity light-grid)
+
+;; part 2
+(define (todo-dimmer inst)
+  (match (instruction-todo inst)
+    ['|turn on| add1]
+    ['|turn off| (λ (x) (max 0 (sub1 x)))]
+    ['|toggle| (curry + 2)]))
+
+(define dimmable-grid (make-vector (* 1000 1000) 0))
+(for ([i (in-list instructions)])
+  (modify-light-grid i dimmable-grid todo-dimmer))
+(apply + (vector->list dimmable-grid))
diff --git a/racket/aoc2015/day-25/day-25.rkt b/racket/aoc2015/day-25/day-25.rkt
new file mode 100644
index 0000000..975f4c3
--- /dev/null
+++ b/racket/aoc2015/day-25/day-25.rkt
@@ -0,0 +1,8 @@
+#lang racket
+
+(define max-r 2978)
+(define max-c 3083)
+
+(for/fold ([code 20151125] [r 1] [c 1]) ([i (in-naturals)] #:break (and (= max-r r) (= max-c c)))
+  (define new-code (modulo (* code 252533) 33554393))
+  (if (= r 1) (values new-code (add1 c) 1) (values new-code (sub1 r) (add1 c))))