First attempt at a faster / more efficient implementation. This is orders of magnitude faster than the first, but still not nearly fast enough.

2018/day12-2.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+
+	"internal/day12"
+	"internal/util"
+)
+
+const NumGenerations = 50000000000
+
+func main() {
+	data := util.ReadInput()
+	plants, rules := day12.FastParseInput(data)
+	rootIndex := 0
+
+	for i := 0; i < NumGenerations; i++ {
+		plants, rootIndex = day12.FastRunGeneration(plants, rules, rootIndex)
+
+		// debug
+		if i%1000000 == 0 {
+			fmt.Println("DEBUG: Generation: ", i)
+		}
+	}
+
+	fmt.Println(day12.FastSumPlants(plants, rootIndex))
+}