last 3 days

23/23.2.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"fmt"
+)
+
+/*
+	This was my third attempt at solving this - the first time trying to work out the
+	pattern of the registers from interpreting the 'assembly'. I gave up on that and
+	turned my input instructions into something closer to very messy go. That didn't
+	quite work either, I had to figure out the register values properly and restructure
+	the loops resulting in the final version below. I found this the most challenging of
+	the puzzles so far - not sure I'd have finished this without some of the hints from
+	the AoC subreddit.
+*/
+
+func main() {
+	f := 0
+	h := 0
+
+	for b := 106500; b <= 123500; b += 17 {
+		f = 1
+		for d := 2; d <= b; d++ {
+			for e := 2; e <= b; e++ {
+				if b%d != 0 { // thanks to AoC reddit for this hint
+					break
+				}
+				if d*e == b {
+					f = 0
+				}
+			}
+		}
+		if f == 0 {
+			h += 1
+		}
+	}
+	fmt.Println(h)
+}