initial commit to day 6 main

1 files changed, 53 insertions, 0 deletions

diff --git a/day2.scm b/day2.scm
new file mode 100755
index 0000000..bb6571f
--- /dev/null
+++ b/day2.scm
@@ -0,0 +1,53 @@
+#!/usr/bin/env gosh
+(use file.util)
+
+(define (read-input filename)
+  (map string->number (string-split (file->string filename) ",")))
+
+(define (run-opcode vec pos)
+  (let ((opcode (vector-ref vec pos)))
+    (cond
+      ((= opcode 1)
+        (vector-set! 
+          vec
+          (vector-ref vec (+ pos 3)) 
+          (+ (vector-ref vec (vector-ref vec (+ pos 1))) 
+             (vector-ref vec (vector-ref vec (+ pos 2)))))
+        (run-opcode vec (+ pos 4)))
+      ((= opcode 2)
+        (vector-set! 
+          vec 
+          (vector-ref vec (+ pos 3))
+          (* (vector-ref vec (vector-ref vec (+ pos 1))) 
+             (vector-ref vec (vector-ref vec (+ pos 2)))))
+        (run-opcode vec (+ pos 4)))
+      ((= opcode 99) vec))))
+
+(define (run-program input noun verb)
+  (let ((input-vector (list->vector input)))
+    (vector-set! input-vector 1 noun)
+    (vector-set! input-vector 2 verb)
+    (vector-ref (run-opcode input-vector 0) 0)))
+
+(define (part1 input)
+  (run-program input 12 2))
+
+(define cartesian-product (lambda (xs ys)
+ (if (or (zero? (length xs)) (zero? (length ys)))
+     '()
+     (fold append '() (map (lambda (x) (map (lambda (y) (cons x y)) ys)) xs)))))
+
+(define (part2 input)
+  (letrec ((nouns (iota 100))
+           (verbs (iota 100))
+           (output (find 
+                    (lambda (x) 
+                      (= 19690720 
+                        (run-program input (car x) (cdr x))))
+                    (cartesian-product nouns verbs))))
+    (+ (cdr output) (* 100 (car output)))))
+
+(define (main args)
+  (let ((input (read-input "inputs/day2.txt")))
+    (print (part1 input))
+    (print (part2 input))))
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