Detecting 3-period oscillators

and properly (?) checking for zero-oscillator stasis.

conway/go/conways-game-of-life/main.go

@@ -20,11 +20,12 @@ var (
 )
 
 func pushChecksum(checksum string, checksums []string) {
-	first2 := make([]string, 2)
+	head := make([]string, 3)
-	copy(first2, checksums[:2])
+	copy(head, checksums[:3])
 	checksums[0] = checksum
-	checksums[1] = first2[0]
+	checksums[1] = head[0]
-	checksums[2] = first2[1]
+	checksums[2] = head[1]
+	checksums[3] = head[2]
 }
 
 func main() {
@@ -37,8 +38,8 @@ func main() {
 		os.Exit(2)
 	}
 
-	checksums := make([]string, 3)
+	checksums := make([]string, 4)
-	checksums[0], checksums[1], checksums[2] = "foo", "bar", "baz"
+	checksums[0], checksums[1], checksums[2], checksums[3] = "foo", "bar", "baz", "qwx"
 	pushChecksum(game.Checksum(), checksums)
 
 	ticks := time.Tick(time.Duration(*sleepMs) * time.Millisecond)
@@ -51,14 +52,20 @@ func main() {
 
 		curChecksum := game.Checksum()
 
-		if checksums[0] == curChecksum {
+		if checksums[0] == curChecksum || checksums[1] == curChecksum {
 			fmt.Println("Stasis!")
 			os.Exit(0)
 		}
 
-		if checksums[1] == curChecksum || checksums[2] == curChecksum {
+		if checksums[2] == curChecksum {
-			fmt.Println("Checksum found in last 2")
+			fmt.Println("Checksum found 2 periods ago")
-			fmt.Println("Stasis with blinkers or beacons or some such!")
+			fmt.Println("Stasis with 2-period oscillator(s)!")
+			os.Exit(0)
+		}
+
+		if checksums[3] == curChecksum {
+			fmt.Println("Checksum found 3 periods ago")
+			fmt.Println("Stasis with 3-period oscillator(s)!")
 			os.Exit(0)
 		}