1 files changed, 32 insertions, 0 deletions
diff --git a/racket/aoc2019/day-02/day-02.rkt b/racket/aoc2019/day-02/day-02.rkt
new file mode 100644
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--- /dev/null
+++ b/racket/aoc2019/day-02/day-02.rkt
@@ -0,0 +1,32 @@
+#lang racket
+
+(require advent-of-code
+         threading)
+
+(define initial-opcodes
+  (parameterize ([current-readtable (make-readtable #f #\, #\space #f)])
+    (port->list read (open-aoc-input (find-session) 2019 2 #:cache #true))))
+
+;; part 1
+(define (edit-opcode ocs oc-1 oc-2)
+  (~> ocs (list-set 1 oc-1) (list-set 2 oc-2)))
+
+(define (run-intcode ocs)
+  (for/fold ([ocs ocs] #:result (car ocs))
+            ([pointer (in-range 0 (length initial-opcodes) 4)] #:break (= 99 (list-ref ocs pointer)))
+    (define op
+      (match (list-ref ocs pointer)
+        [1 +]
+        [2 *]))
+    (list-set ocs
+              (list-ref ocs (+ 3 pointer))
+              (op (list-ref ocs (list-ref ocs (+ 1 pointer)))
+                  (list-ref ocs (list-ref ocs (+ 2 pointer)))))))
+
+(~> initial-opcodes (edit-opcode 12 2) run-intcode)
+
+;; part 2
+(for*/first ([noun (inclusive-range 0 99)]
+             [verb (inclusive-range 0 99)]
+             #:when (~> initial-opcodes (edit-opcode noun verb) run-intcode (= 19690720)))
+  (+ (* 100 noun) verb))