day20, examples work in test

day20/propagation_test.go

@@ -93,3 +93,13 @@ func TestPropagateButtonPressExample2FourSteps(t *testing.T) {
 	}
 
 }
+
+func TestExample1TheQuestion(t *testing.T) {
+	filename := "example1"
+	modules := ReadModules(filename)
+	InitStuffs(modules)
+
+	low, high := Count10000ButtonPresses(modules)
+	t.Log("got low and high: ", low, high)
+	t.Log("response is: ", low * high)
+}

day20/pulsePropagation.go

@@ -15,11 +15,54 @@ func Run() int {
 	InitStuffs(modules)
 	log.Print("got modules:\n", modules)
 
-	low, high := PropagateButtonPress(modules)
+	low, high := Count10000ButtonPresses(modules)
 	log.Printf("got low %d and high %d\n", low, high)
-	log.Print("modules after single button press:\n", modules)
 
-	return 0
+	return low * high
+}
+
+func Count10000ButtonPresses(modules map[string]Module) (lowSignalsCount, highSignalsCount int) {
+	count := 10000
+	type counts struct {
+		low, high int
+		step int
+	}
+	countsAfterState := make(map[string]counts)
+	// after each button press check if reached already known state - cycle is present.
+	// then calculate amount of signals before the loop - how much was on that previous state.
+	// then diff - how much added after the loop
+
+	// for now let's just print the info on loop
+
+	for i := 0; i < count; i++ {
+		stepLow, stepHigh := PropagateButtonPress(modules)
+		lowSignalsCount += stepLow
+		highSignalsCount += stepHigh
+		log.Printf("after step %d low is %d and high is %d", i, lowSignalsCount, highSignalsCount)
+		state := ModulesState(modules)
+
+		prevCounts, found := countsAfterState[state]
+		if found {
+			loopLen := i - prevCounts.step
+
+			log.Printf(">>> found loop. from step %d to step %d. of len %d",
+				prevCounts.step, i, loopLen)
+
+			multiplication := count / loopLen
+
+			lowCountInCycle := lowSignalsCount - prevCounts.low
+			highCountInCycle := highSignalsCount - prevCounts.high
+
+			lowSignalsCount = lowCountInCycle * multiplication
+			highSignalsCount = highCountInCycle * multiplication
+
+			return
+		}
+
+		countsAfterState[state] = counts{stepLow, stepHigh, i}
+	}
+
+	return
 }
 
 func PropagateButtonPress(modules map[string]Module) (lowSignalsCount, highSignalsCount int) {